After a three-day trial, the jury found appellant guilty of armed robbery1 and possession of a firearm during a crime of violence2 (“PFCV”).3 The trial court sentenced appellant to 108 months followed by five years of supervised release for each crime, to be served concurrently. This court consolidated appellant’s direct appeal and his appeal from the trial court’s denial of his § 23-110/new trial motion. Appellant argues on direct appeal that the trial court erred by (1) refusing to allow appellant to present an expert witness on the subject of identification testimony, (2) failing during trial to conduct an appropriate inquiry into appellant’s dissatisfaction with defense counsel’s conduct, and (3) failing to correct the government’s assertedly impermissible closing argument that appellant’s defense was “malarkey” and “garbage,” sua sponte. Appellant also contends that the trial court erred in denying his § 23-110 motion without a hearing on appellant’s allegation of ineffective assistance of counsel based on his attorney’s failure to present evidence regarding his hand tattoo and failing to investigate another suspect’s claim of guilt of the crime.4 We disagree and affirm.
I.
At approximately 6:30 PM on April 11, 2007, near 31st Street and Avon Lane, a man, whose face was unobstructed, approached the victim, Mira Kuczynska, within three to four feet. The man mumbled what sounded like “this is a robbery,” and he displayed a “western-style” revolver with a brown and dark yellow handle in his waistband. After approximately ten seconds, the man grabbed her purse and then ran off. Her purse contained, among other things, her wallet, credit cards, identification, a checkbook, and mobile phones.
After the incident, Ms. Kuczynska described the ,man to police as an African-American male in his late twenties or thirties who was about six feet tall,5 thin-figured, with a medium skin complexion, and short hair with some facial hair. Shortly thereafter when police stopped a person for Ms. Kuczynska to perform a *235show-up identification, she stated that the person the police presented to her was not the one who robbed her.
After the robbery a number of significant events occurred. Approximately twenty minutes after the robbery, Monica Barnes, a person that appellant, while being interviewed by police, characterized as his girlfriend, placed a phone call using Ms. Kuczynska’s cellular telephone. A Giant store video surveillance revealed that on April 14th, 2007, Monica Barnes alighted from a silver minivan in a Giant food store parking lot in Laurel, Maryland, entered the store, and used an altered check belonging to Ms. Kuczynska to purchase gift cards. Approximately twenty minutes later, appellant, wearing a multi-colored sweater-jacket, returned to the same cashier to purchase a large amount of gift cards with another one of Ms. Kuczynska’s altered checks, but the store detective refused to accept the check and escorted appellant out of the store. Appellant entered a silver minivan in the parking lot and drove off with Monica Barnes. On April 19, 2007, Anthony Gain, accompanied by his girlfriend and appellant, returned a silver Dodge Caravan minivan to Progressive Rent-a-Car that he had rented three days earlier. The three were arrested by Laurel police. Assisted by D.C. Metropolitan Police Department (“MPD”) detectives, Laurel police interviewed appellant, who provided information leading to a Motel 6 location in Laurel.
Police obtained a search warrant to search the Motel 6 room. When they arrived at the motel, its guest registry reflected that the motel management had rented a room to Ms. Kuczynska.6 MPD Detectives Michael Ross and Keith Tabron went to the room and after knocking on the door and announcing their presence and purpose, Monica Barnes opened the door. One Jarwon Scott was inside.7 In the room police recovered a multi-colored jacket appearing to be the same jacket worn by appellant in the surveillance tape from the Giant food store. Inside the jacket was a prescription bottle belonging to a person named “Franklin Powell,” the same name used by appellant to introduce himself to the police in his interview on April 19th.8 Police seized a cell phone, personal check,9 and a credit or debit card — all Ms. Kuczynska’s stolen property. A black, .38 caliber revolver with a brown handle — similar to the description provided by Ms. Kuczynska — was hidden under the mattress. Police also located a Giant store receipt and an identification card with a photograph of Barnes and Ms. Kuc-zynska’s name on it.
Nine days after the robbery, Ms. Kuc-zynska identified appellant in a photo array and stated she was positive that appellant was the robber. She also identified appellant at trial. As will be seen later, there is significance to the fact that a motion to suppress photo identification was denied and that issue is not presented on this appeal.
*236II.
A. Direct Appeal
1. Expert Testimony
Prior to the beginning of the first of his three trials, appellant filed a motion seeking leave to introduce expert testimony of Dr. Henry Shulman, a professor of psychology at Ohio State University, “on psychological factors of memory and perception that may affect the accuracy of eyewitness identifications.” The government filed a “motion in opposition” to the expert testimony arguing that the victim’s identification was corroborated by the fact that appellant was arrested in a vehicle containing some of Ms. Kuczynska’s stolen property, appellant was seen on the Giant store surveillance video attempting to pass checks in Ms. Kuczyns-ka’s name, and because appellant sent police to the motel room where more of Ms. Kuczynska’s stolen property was located.
The trial judge denied the motion, distinguishing appellant’s case from past cases where he had admitted such testimony. For the court, the key distinction was that cases where the court had admitted expert testimony in the past were ones where there was little corroborating evidence; in those cases, the court reasoned, expert testimony on identification “would [have been] helpful to the [jury]” on cross-racial identification. In appellant’s case, the court concluded:
[W]ith respect to eyewitness identification I have ruled previously in cases that — having heard from Dr. Schulman (phonetic) that on a very narrow issue of cross racial (phonetic) identification I have permitted expert testimony in that area where the government didn’t have much other evidence in the case and I thought it would be of assistance to the trier of fact. I thought Dr. Schulman has demonstrated to me there was sufficient basis under Dias (phonetic) to admit the testimony in one — maybe two cases I’ve tried. I do remember one where there is very little corroborative evidence in the case and there was sufficient evidence. I thought the testimony about cross racial identification would be helpful to the trier of fact.... [T]he calculus in this case is a little bit different. This is certainly not one of those cases where I think, you know, the issue of cross racial identification is one that I think needs to be explored by an expert. There is abundant corroborative evidence in this case with regard to demonstrating Mr. Patterson’s involvement in these offenses. He was observed cashing some of these check in another jurisdiction or trying to pass those checks. A room that’s associated with him in Maryland. There are proceeds of the robbery that were found in that room. It was his girlfriend’s room apparently but he was associated with that room in Maryland. He was identified in a vehicle that’s been associated with those robberies. In a case like this I think that weighing the probative value versus prejudice having an expert testify in a case like this would put an unnecessary (indiscernible) on his opinion testimony and I’m not prepared to admit the testimony in this type of case. I have done it in other cases where the government had little or no other corroborative evidence and I thought it would be helpful to the trier of fact.
Moreover, the trial court added, the standard jury instruction would provide the jury “with all the guidance it needs to be able to determine the accuracy and reliability of eyewitness identification.” Finally, the witness would be impermissibly involved in the jury reaching its “ultimate opinion about the reliability of the identification and give undue weight to [the ex*237pert’s] opinion in the narrow area of cross racial identification.” During appellant’s second trial, presided over by a different judge, appellant renewed his request to introduce expert testimony, but that trial judge, too, denied the motion, stating that it had no reason “to revisit what was a ... perfectly reasonable discretionary decision by [the previous trial judge].”10
Appellant contends that the first trial court erred when it refused to permit appellant to present an expert witness on identification testimony. Appellant argues that the first trial court failed to exercise its discretion by basing its decision on corroborative evidence, which is not part of the Dyas test. See Dyas v. United States, 376 A.2d 827, 832 (D.C.1977).11 He also asserts that the second trial court’s acceptance of the ruling of the first trial court was erroneous because some of the “corroborative evidence [relied upon by the first trial judge] was different than that which the [third trial judge] based his decision to exclude [the expert testimony].”
We begin this part of the opinion by observing that appellant’s assertion that corroborative evidence relied on by the first trial judge was different than that relied on by the third trial judge is belied by the record because all of the corroborative evidence referred to by the first trial court, save one minor fact,12 was admitted during the third trial.
Although some observe that the initial decision whether to admit or exclude expert testimony must be made in a vacuum, there is logic to stating that this particular proffer of asserted expert testimony could reasonably be evaluated in light of the government’s opposition outlining corroborative facts establishing appellant’s identity.13 This is so because the funda*238mental inquiry is whether the asserted expert testimony would assist the jury in rendering its verdict. See, e.g., Smith v. United States, 27 A.3d 1189, 1195 (D.C.2011) (“[T]he decision to exclude expert evidence must be made on a case-by-case basis, grounded on the proffer made and on its potential to assist the jury in the particular case before the court.” (alteration in original) (internal quotation marks omitted)); Benn v. United States (Benn II), 978 A.2d 1257, 1274 (D.C.2009) (“As we emphasized in Green [v. United States, 718 A.2d 1042, 1051 (D.C.1998) ], the decision to admit or exclude expert testimony must be made on a case-by-case basis, grounded on the proffer made and on its potential to assist the jury in the particular case before the court.”); Hager v. United States, 856 A.2d 1143, 1147 (D.C.2004) (“Thus, [i]n a jury trial the judge must exercise discretion to decide whether the proffered expert testimony is likely to assist the jury in the performance of its duties — that is to say, in understanding the evidence, determining the facts that must be found and rendering its verdict.” (internal quotation marks omitted)); Green, supra, 718 A.2d at 1051 (“Surely it would be unnecessary and undesirable to present expert testimony in each and every case involving eyewitnesses, but there may be cases in which a jury would find such testimony helpful.” (footnote omitted)). We fully respect our colleague’s view that under some, but not all circumstances, this type of testimony should be admitted when the jury requires assistance in deciding the verity of an identification. But, this issue, in discrete cases, must be tested on whether it was an erroneous exercise of discretion exercised under all circumstances present, not under a rule that such testimony must always be admitted because jurors are not fit to decide the issue unaided by expert testimony. When other evidence points to the verity of a victim’s identification of the accused, such as the victim’s depiction of the gun in a sketch immediately after the crime and the police’s recovery of a gun in the motel matching that description, that evidence is a legitimate consideration for the trial judge in exercising judgment on whether to exclude such expert testimony. Life experiences are sufficient and a trial judge must be vested with discretion to sort out the various situations where experts may illuminate the question.
In short, one may argue that the Dyas test does not include corroboration. And they would be correct. But our inquiry does not end there. Because we review the trial court’s exercise of its discretion in *239the exclusion of expert testimony for an abuse of discretion, our caselaw holds that the existence of corroborative evidence is probative of the verity of the trial court’s decision-making.14 See Benn II, supra, 978 A.2d at 1280; Hager, supra, 856 A.2d at 1149.15 Here, the evidence as proffered, and as admitted at trial, hardly left the verity of identification of appellant as the actual robber beyond the ken of the jury. Cf. Benn II, supra, 978 A.2d at 1268 (concluding that although jurors “are not fully aware of the factors that influence eyewitness testimony,” “[cjertain factors that can influence an eyewitnesses’ observation and recall are familiar to lay persons [including] cross-racial identifications” (internal quotation marks omitted)).
What is said above on this issue is hardly dicta as the concurrence asserts. It is necessary to our decision that the correct decisional law be stated so the trial court and the Bar are not confused by the concurrence, which views the proffered testimony as intrinsically or automatically admissible upon a determination of relevance. Indeed, the concurrence looks only to relevance, and jumps from that to the conclusion that discretion to deny admission of the testimony is abused unless the “error” is deemed harmless. It leaves no room for considering other evidence which alleviates the need to assist the jury in deciding the issue of identity. That predicate is not available to a division of the Court until, and if, the en banc court overturns the holdings of many decisions leaving to the trial judges whether, from all the evidence proffered or received, the jury will be assisted, confused or awed by the expert testimony. See M.A.P. v. Ryan, 285 A.2d 310 (D.C.1971).
However, in the interest of unanimity as to the result, we may, as the concur*240rence does, take the course of least resistance by assuming that if error there be, it was harmless, accord, Benn II, supra, 978 A.2d at 1283 (“In a case grounded on eyewitness identifications of a stranger, without other corroborating evidence, and in which the defense depends entirely upon demonstrating that the identifying witnesses are not as reliable as they believe themselves to be, to preclude the defendant from presenting the scientific testimony of a qualified expert on research that is generally accepted and not known to lay jurors to prove this point is not harmless under Kotteakos .... ” (emphasis added)). See generally Kotteakos v. United States, 328 U.S. 750, 765, 66 S.Ct. 1239, 90 L.Ed. 1557 (1946).
Here, the corroborative evidence establishing the accuracy of the victim’s identification of appellant is quite notable, thus making any assumed error as to expert testimony harmless. It included Ms. Kuc-zynska’s description of the perpetrator matching appellant and not Jarwon Scott,16 Ms. Kuczynska’s declining to identify a suspect as the perpetrator in a show-up immediately after the crime, her identification of appellant in the photo array, and the fact that appellant’s effort to put the actual robbery at the hands of another in the gang would not have established actual innocence, but rather as one who shared in the spoils of the robbery by receiving the stolen property. In addition, Ms. Kuc-zynska had no opportunity to view the appellant other than during the crime, during the only photo array, and during trial. All of this justifies a harmlessness holding in this case. It is also noteworthy that appellant fails to pursue the effort to suppress the photo identification. Thus for our purposes the reliability of Ms. Kuc-zynska’s identification is further enhanced because there is no probability of an irreparable misidentification. See, e.g., West v. United States, 866 A.2d 74, 82-83 (D.C.2005).
2. Right to Present a Defense
Appellant also argues that by excluding his expert testimony, the trial court denied him his constitutional right to present a defense. In Heath v. United States, we expounded on the meaning of the right to present a defense. There we noted that “[t]he Constitution guarantees a criminal defendant a meaningful opportunity to call witnesses in order to present a complete defense.” Heath v. United States, 26 A.3d 266, 275 (D.C.2011). But “ ‘[t]he accused does not have an unfettered right to offer testimony that is incompetent, privileged, or otherwise inadmissible under standard rules of evidence,’ and ... ‘trial judges [may] exclude evidence if its probative value is outweighed by ... unfair prejudice, confusion of the issues, or potential to mislead the jury.’ ” Id. at 276 (footnote omitted). “Rulings excluding (or admitting) evidence ordinarily are within the ambit of the trial court’s discretion and are subject to review only for abuse of that discretion under the Kotteakos standard of harmlessness.” Id. “It is the ‘rare’ case in which a trial court’s ‘application of a rule of evidence is so erroneous and unfair’ as to deprive a defendant of a meaningful opportunity to present a complete defense.” Id.
The evidence is also subject to “a materiality requirement,” meaning that “a defendant must demonstrate that the excluded evidence was important to his de*241fense in order to show that the error was of constitutional magnitude.” Id. at 277 (internal quotation marks omitted). “[I]t must be reasonably probable (and not merely possible) that the jury would have harbored a reasonable doubt regarding the defendant’s guilt if the evidence had [been admitted].” Id. at 280. This standard is less demanding than the preponderance-of-the-evidence test. Id. As the Heath Court explained: “The question is not whether the defendant would more likely than not have received a different verdict with the evidence, but whether in its absence he received a fair trial, understood as a trial resulting in a verdict worthy of confidence.” Id.
Here, appellant was not denied a meaningful opportunity to present a defense. Appellant presented Monica Barnes in his defense, and Barnes corroborated appellant’s argument of misidentifí-cation by stating that Ms. Kuczynska’s book of checks and cell phone were given to her by Scott and Gain, not appellant. Moreover, the trial court did not prevent appellant from arguing that the witness misidentified appellant. Appellant “conducted ample cross-examination of Ms. [Kuczynska] on her ability to observe” the face of her assailant. Id. at 284. Appellant also argued, during closing argument, that stranger identification is less reliable, and that Ms. Kuczynska did not have enough time to observe appellant and focused on the gun instead. Given appellant’s extensive presentation of his mis-identification through argument and a witness, we conclude that the trial court did not violate appellant’s constitutional right to present a defense. “We find it highly probable that the trial court’s ruling did not influence the jury’s verdict; we see no reasonable probability that the expert’s testimony would have engendered an otherwise-nonexistent reasonable doubt of appellant’s guilt in the juror’s minds.” Id. at 275.
3. Monroe-Farrell Claim
We now turn to appellant’s argument that the trial court should have conducted a Monroe-Farrell inquiry because of “trial counsel’s motion to withdraw filed [after the first trial, but] prior to the second trial.” Appellant contends that as a result of that motion between the first and third trial, the third trial court should have made an inquiry into the relationship between counsel and appellant during the third trial when appellant stated to the court that he “could do better as [his] own lawyer.” This argument does not persuade us.
Under Monroe-Farrell, appellant would have needed to make a “pretrial challenge to the effectiveness of counsel,” see Moore v. United States, 675 A.2d 71, 74 (D.C.1996) (quoting Monroe v. United States, 389 A.2d 811, 820 (D.C.1978)), and appellant’s satisfaction with counsel, as noted on the record, fails to be a challenge to counsel. The basis of appellant’s challenge appears actually to be something that occurred during the previous trial. Moreover, “[a]ny claim of ineffectiveness must be specific and detailed; ‘[g]eneral assertions that a defendant wants a new lawyer are not enough to trigger a Monroe-Farrell [v. United States, 391 A.2d 755 (D.C.1978) ] inquiry.’ ” Oliver v. United States, 832 A.2d 153, 157 (D.C.2003) (quoting Matthews v. United States, 629 A.2d 1185, 1191 (D.C.1993)).
4. Right to Proceed Pro Se
Appellant also argues that the trial court erred because it did not “conduct an appropriate inquiry” into trial counsel’s performance after appellant’s statement that he “could do a lot better as [his] own *242lawyer.” We find no error by the court as to this contention.
Although “[a] defendant has a Sixth Amendment ‘constitutional right to conduct his own defense,’ ” Hill v. United States, 959 A.2d 702, 708 (D.C.2008) (quoting Faretta v. California, 422 U.S. 806, 836, 95 S.Ct. 2525, 45 L.Ed.2d 562 (1975)), a court will not recognize a defendant’s desire to proceed pro se unless the defendant “make[s] a positive demand upon the trial court for leave to proceed without counsel.” Perry v. United States, 364 A.2d 617, 620 (D.C.1976). “In view of the fact that appellant did not at any time make a positive demand upon the trial court for leave to proceed without counsel, we are unable to find substance in his contention that Faretta provides cause for reversal.” Perry, supra, 364 A.2d at 620. Appellant’s statement was, at most, an expression of frustration with his attorney, not a clear and unequivocal declaration of a desire to represent himself to a judge.
5. Prosecutorial Argument Claim
Appellant argues that the trial court erred by not, sua sponte, correcting the government’s assertedly improper comment during closing argument. Referring to appellant’s use of Monica Barnes as a defense witness, the government stated during closing argument: “That is a bunch of malarkey. Frankly, shame on the [appellant] for putting his girl friend on the stand to try to sell you that garbage.... All of the evidence points to [appellant].” The government went on to describe the corroborative evidence. Appellant contends that, by using the term “malarkey,” the government characterized appellant as a liar. The government’s argument, appellant continues, also represented improper personal belief by the prosecutor.
“If appellant did not object, then our review is for plain error.” Washington v. United States, 884 A.2d 1080, 1088 (D.C.2005). Under plain error review, appellant bears the burden of proving “(1) error, (2) that is plain, and (3) that affected appellant’s substantial rights. Even if all three of these conditions are met, this court will not reverse unless (4) the error seriously affects the fairness, integrity, or public reputation of judicial proceedings.” Lowery v. United States, 3 A.3d 1169, 1173 (D.C.2010) (internal quotation marks omitted). Plain error is error that was “clear or obvious,” and this is a formidable burden. Comford v. United States, 947 A.2d 1181, 1189 (D.C.2008) (internal quotation marks omitted).
We evaluate claims of improper prosecutorial argument by first determining whether or not the challenged argument was improper. See, e.g., Finch v. United States, 867 A.2d 222, 225 (D.C.2005). As this court has repeatedly stated, “[i]t is improper for a lawyer to express a personal opinion about a witness’ veracity [or credibility] during arguments to the jury.” Id. at 226 (internal quotation marks omitted). Yet, “it is proper for an advocate to argue that the evidence supports the conclusion that a witness is incredible.” Id. The central distinction is “whether the attorney is commenting on the evidence, which he may do, or expressing a personal opinion, which is taboo. A comment will be within the acceptable range as long as it is in the general nature of argument, and not an outright expression of opinion.” Irick v. United States, 565 A.2d 26, 36 (D.C.1989).
“Under the circumstances, including the strength of the government’s case, we cannot conclude that the judge ... plainly erred.” Finch, supra, 867 A.2d at 228. The government having argued from the evidence, there is nothing improper about the use of the words “malarkey” or *243“garbage.” Any dictionary definition of those terms will show just what the prosecutor was suggesting — foolish talk or worthless talk. See, e.g., Collins English Dictionary-Complete & Unabridged (10th ed. 2009); Webster’s Third New International Dictionary of the English Language Unabridged (1993); Merriam-Webster’s Collegiate Dictionary (10th ed. 1993); see also Soto v. Commonwealth, 139 S.W.3d 827, 875 (Ky.2004); State v. Williams, 133 Ariz. 220, 650 P.2d 1202, 1211-12 (1982). As this Court has put it: “[the prosecutor] is not required to be boring.” See Irick v. United States, 565 A.2d 26, 37 (D.C.1989). The arguments were made in the context of the overwhelming corroborative evidence in the case and, in all likelihood, had very little effect on the outcome of the trial. The government’s attorney was attempting to discredit the appellant’s misidentification defense and reinforce Ms. Kuczynska’s identification of the appellant by showing that appellant and Scott were physically distinguishable. This was a reasonable inference from the evidence.
B. § 23-110 Appeal
In an appeal of the denial of his § 23-110 motion without a hearing, appellant asserts that the court incorrectly concluded that appellant’s allegations in his § 23-110 motion, even if true, would merit no relief. Specifically, appellant argues that defense counsel was ineffective because counsel failed to pursue Jarwon Scott’s alleged admission to the April 11th robbery for presentation at trial and failed to present evidence of appellant’s distinctive hand tattoo.
“We review the trial court’s denial of appellant’s D.C.Code § 23-110 motion without a hearing for an abuse of a discretion.” Freeman v. United States, 971 A.2d 188, 201 (D.C.2009). “To uphold the denial of [appellant’s D.C.Code] § 23-110 motion without a hearing, this court must conclude that under no circumstances could [appellant] establish facts warranting relief.” Id. (alteration in original) (internal quotation marks omitted). “Although a hearing is particularly appropriate when ineffective assistance of counsel is alleged, an evidentiary hearing is not required in every case.” Id. Specifically, a hearing is not necessary “[w]hen ‘the motion and files and records of the case conclusively show that the prisoner is entitled to no relief.’ ” D.C.Code § 23-110(c); Freeman, supra, 971 A.2d at 201. A court may summarily dismiss claims that are (1) vague and con-clusory or (2) palpably incredible or (3) that would not merit relief even if true. Id. (internal quotation marks omitted).
“An appellant alleging the constitutional ineffectiveness of his trial counsel must demonstrate both deficient performance and prejudice in order to merit relief under D.C.Code § 23-110.” Id. (citing Strickland v. Washington, 466 U.S. 668, 687, 104 S.Ct. 2052, 80 L.Ed.2d 674 (1984)). Deficient performance requires a showing “that counsel made errors so serious that counsel was not functioning as the ‘counsel’ guaranteed the defendant by the Sixth Amendment.” Jones v. United States, 918 A.2d 389, 402 (D.C.2007) (quoting Strickland, supra, 466 U.S. at 687, 104 S.Ct. 2052 (1984)) (internal quotation marks omitted). In assessing counsel’s performance we must determine “whether counsel’s assistance was reasonable considering all the circumstances.” In re R.E.S., 978 A.2d 182, 192 (D.C.2009) (quoting Strickland, supra, 466 U.S. at 688, 104 S.Ct. 2052) (internal quotation marks omitted). Appellant must demonstrate prejudice by showing “there is a reasonable probability that, but for counsel’s unprofessional errors, the result of the proceeding would have been different.” Jones, *244supra, 918 A.2d at 402 (internal quotation marks omitted). “[J]udicial scrutiny of counsel’s performance must be highly deferential .... A fair assessment of attorney performance requires that every effort be made to eliminate the distorting effects of hindsight, [and] ... a court must indulge a strong presumption that counsel’s conduct falls within the wide range of reasonable professional assistance.... ” In re R.E.S., supra, 978 A.2d at 192 (quoting Strickland, supra, 466 U.S. at 689, 104 S.Ct. 2052) (internal quotation marks omitted).
Appellant argues that Jarwon Scott’s claim of responsibility for the April 11th robbery in an affidavit submitted with the § 23-110 motion, well after the end of the third trial, would have been sufficient to cast doubt on the outcome of the third trial even though the trial judge in the third trial only had access to a different, unsworn letter written by Scott. A careful reading of the two letters demonstrates that appellant’s claims, even if true, would have merited no relief. In the unsworn letter Scott stated “[Appellant] did not have anything to do with what I did back in April, which I have taken full responsibility for, and I am doing so now realizing that I was being selfish thinking about myself in which I have committed the crime and have accepted my punishment.” We do not know what charges against appellant Scott was aware of for the third trial, and Scott’s knowledge is relevant because appellant and Scott were tried for many of the same April crimes during appellant’s first trial. Coupled with Scott’s usage of the past tense form of “accept” while describing his acceptance of his punishment for the April 17th crimes (for which he pled guilty), the most natural reading of the unsworn letter is Scott taking responsibility for the April 17th crimes and not appellant’s April 11th crime. Scott submitted a sworn affidavit after the third trial was completed, but before the trial court heard the § 23-110 motion, in which he implicated himself and absolved appellant of the April 11th crime. Yet, since appellant could not have used Scott’s subsequent affidavit during the third trial, Scott’s unsworn, vague letter, which was submitted before the third trial could not have changed the outcome of the trial. Moreover, because Scott’s attorney prevented appellant’s attorney from interviewing Scott at all during the trial, appellant cannot demonstrate prejudice by showing “there is a reasonable probability that, but for counsel’s unprofessional errors, the result of the proceeding would have been different.” Jones, supra, 918 A.2d at 402 (internal quotation marks omitted).17
Appellant also argues that counsel was ineffective for failing to present evidence of appellant’s hand tattoo at trial in order to undermine Ms. Kuczynska’s failure to mention the tattoo in her eyewitness identification. Appellant adds that a number of correction officers could have testified that appellant had the hand tattoo prior to the robbery. Considering all the circumstances, including, inter alia, the limited probative value of the hand tattoo, the uncertainty as to the victim’s memory with respect to the tattoo, and the potential prejudice to appellant of the testimony of former law enforcement officials, counsel’s performance was neither deficient nor prejudicial to appellant. Thus, “[b]ecause the allegations contained in appellant’s motion can fairly be characterized as falling into the[ ] [three] categories [providing for the denial of a § 23-110 motion without a *245hearing], we find no error by the trial judge in denying the motion without a hearing.” Freeman, supra, 971 A.2d at 201.
Accordingly, appellant’s convictions are affirmed and the order denying the collateral attack without a hearing is affirmed.
So ordered.
. D.C.Code § 22-2801 (2001); D.C.Code § 22-4502 (2011 Supp.).
. D.C.Code § 22-4504(2001).
. This appeal comes from appellant's third trial. In appellant’s first trial appellant was tried for two counts of armed robbery, one count of assault with intent to rob while armed, four counts of PFCV, and one count of assault with a dangerous weapon. The trial court declared a mistrial because the government was unable to produce a key witness— Jarwon Scott. In appellant's second trial, the government proceeded only on one count each of armed robbery, assault with intent to rob while armed, and PFCV. The second trial resulted in a hung jury mistrial.
. D.C.Code § 23-110(2001).
. The record shows that appellant was 6'3" tall.
. Barnes also admitted that she rented the room with an American Express gift card she purchased with Ms. Kuczynska’s altered check. Barnes was charged with forgery in Prince George’s County, Maryland for this crime.
. Scott is a youthful-looking man, approximately 5'5" tall, with a light brown skin complexion, a dreadlocks hairstyle, and barely any facial hair.
. Barnes also said that appellant used the alias Franklin Powell.
. Barnes claimed that Gain and Scott provided her with the cell phone and the checkbook on April 11th. Gain claimed he did not know anyone named Jarwon Scott and he did not recognize photos of Scott or Barnes.
. As the judge in the third trial was the same judge who presided over the second trial, appellant did not renew the motion before the third trial began, and the government does not argue that appellant needed to renew the motion in order to preserve the claim for this appeal. For purposes of this appeal we treat the claim as preserved with this caveat: the first trial judge left this matter open for reconsideration if “there isn't as much corroboration as [he] initially thought.” Since the appellant did not ask Judge Richter to reconsider what had been left open to him, it is not helpful to the concurrence to fault his analysis in maintaining the refusal of the expert proffer.
. In Dyas, this court determined that in order to admit expert testimony: (1) the subject matter must be so distinctively related to some science, profession, business or occupation as to be beyond the ken of the average layman; (2) the witness must have sufficient skill, knowledge or experience in that field or calling as to make it appear that his opinion or inference will probably aid the trier in his search for truth; and (3) expert testimony is inadmissible if the state of the pertinent art or scientific knowledge does not permit a reasonable opinion to be asserted even by an expert. See Dyas, supra, 376 A.2d at 832.
. The first trial court cited to the fact that appellant was associated with the vehicle which was also associated with an April 17th robbery, a crime the government attempted to prosecute appellant of during the first trial and for which, another person, Jarwon Scott, pled guilty.
. Cf. Benn v. United States (Benn II), 978 A.2d 1257, 1280 (D.C.2009) ("[W]here ... corroboration of identification exists, the exclusion of ... proffered expert testimony by the trial court generally does not constitute an abuse of discretion.”); Hager v. United States, 856 A.2d 1143, 1149 (D.C.2004) (”[I]n cases where ... corroboration of identification exists, the exclusion of the proffered expert testimony by the trial court generally does not constitute an abuse of discretion.”). In Benn II, we factually distinguished Hager and Green v. United States, 718 A.2d 1042 (D.C.1998), and the persuasiveness of our reasoning in distinguishing those cases endures. In Hager, in addition to the eyewitness testimony being irrelevant because it was based on problems in stranger identification and Hager knew the *238eyewitnesses, there was physical evidence against Hager. See Benn II, supra, 978 A.2d at 1280; Hager, supra, 856 A.2d at 1149. We also thought it was important to observe that we were “aware of no published opinion of this court, since our decision in Brooks [v. United States, 448 A.2d 253 (D.C.1982) ] twenty-seven years ago, affirming the exclusion of expert testimony on eyewitness identifications in a case in which the only evidence presented against the defendant was the identification of eyewitnesses who did not know the defendant.” Benn II, supra, 978 A.2d at 1280 (emphasis added). The present case is in accord with Benn IVs observations about our opinions after Brooks. We also took the opportunity to distinguish Green because of corroborating physical evidence. Id. at 1281. Here, unlike Benn in Benn II, the substantial amount of corroborative evidence does not, upon, "closer scrutiny [,] place [] the strength of the case in substantial doubt." Cf. id. at 1282 (concluding that the evidence, upon "closer scmtiny, places the strength of the case in substantial doubt" because the five disinterested witnesses merely said that Benn “looked like” the perpetrator during the photo spread, three of which stated they were "95%” sure, and all five identified Benn in court). It should be noted, further, that we are not bound by the dicta of our previous opinions, but only by rules of law adopted as a part of decisions. See In re D.T., 977 A.2d 346, 352 n. 1 (D.C.2009).
. The concurrence acknowledges this, stating "I readily grant that where a challenged identification is corroborated, the appellate court may be able to conclude that the erroneous exclusion of expert testimony on eyewitness identification was harmless, and hence that there was no 'abuse' of discretion.” The concurrence also points out that the expert testimony was, at the very least, relevant. This is, undoubtedly, correct. However, our examination of a trial court’s exercise of discretion in the admission or exclusion of expert testimony, does not end there. See, e.g., Smith v. United States, 27 A.3d 1189, 1195 (D.C.2011) ("Generally, expert testimony should be admitted if it is relevant and likely to aid the trier of fact in the search for the truth.” (internal quotation marks omitted)); note 11 supra, (setting forth the Dyas test on the admissibility of expert testimony).
. A number of jurisdictions also reach this conclusion. See, e.g., United States v. Crotteau, 218 F.3d 826, 833 (7th Cir.2000) ("[Wjhen there is corroborating evidence, expert testimony regarding the reliability of eyewitness identification is not necessaiy.”); Comm. v. Watson, 455 Mass. 246, 915 N.E.2d 1052, 1062 (2009) ("Where there is additional evidence to corroborate an eyewitness’s identification, a judge does not overstep the bounds of discretion in excluding expert testimony.”); Comm. v. Santoli, 424 Mass. 837, 680 N.E.2d 1116, 1119 (1997) ("[Ojpinions that rule that the exclusion of the expert testimony was or may have been error are typically those where there was little or no evidence to corroborate the eyewitness identification.”); People v. LeGrand, 8 N.Y.3d 449, 835 N.Y.S.2d 523, 867 N.E.2d 374, 381 (2007) ("In the event that sufficient corroborating evidence is found to exist, an exercise of discretion excluding eyewitness expert testimony would not be fatal to a jury verdict convicting defendant.”); accord, Johnson v. State, 272 Ga. 254, 526 S.E.2d 549, 552-53 (2000) ("Where eyewitness identification of the defendant is a key element of the State’s case and there is no substantial corroboration of that identification by other evidence, trial courts may not exclude expert testimony without carefully weighing whether the evidence would assist the jury in assessing the reliability of eyewitness testimony and whether expert eyewitness testimony is the only effective way to reveal any weakness in an eyewitness identification.” (footnote omitted)).
. As discussed infra, appellant also asserts that Scott took responsibility for both crimes. As repeatedly pointed out at trial, however, appellant and Scott look almost nothing alike. Scott was a young-looking, short, beardless man with a dreadlocks hairstyle, and was 5'5." Appellant's appearance is different. See note 5 and accompanying text, supra.
. Appellant also fails to demonstrate prejudice because even if Scott had taken the stand, the prosecutor could have impeached Scott with prior statements made by Scott incriminating appellant.