On October 10, 1972, appellant was sentenced to life imprisonment, having been convicted on a two-count indictment of the offense of murder. A co-defendant and alleged accomplice was also convicted of the same charge. See, Adams v. State, (1974) *773262 Ind. 220, 314 N.E.2d 53. Subsequently appellant filed his petition for post-conviction relief in Allen Circuit Court. This is an appeal from an adverse decision on that petition.
Appellant first claims the trial court erred in granting the State’s motion to strike that part of appellant’s petition referring to certain errors that allegedly occurred during appellant’s trial. The post-conviction judge stated in his findings of fact, “[T]he allegations in these paragraphs were stricken for the reason that said issues so raised had been adjudicated by the Supreme Court of Indiana in Adams v. State, 262 Ind. 220, 314 N.E.2d 53.”
An examination of appellant’s petition shows, as the court observed, all stricken portions are among the errors alleged by the appellant in his Motion to Correct Errors filed after the original trial. All these allegations of error were treated by this Court in the direct appeal and were decided adversely to appellant. Issues raised and determined on direct appeal are not reviewable in a post-conviction proceeding. Kennedy v. State, (1979) Ind., 393 N.E.2d 139; Eliacin v. State, (1978) 269 Ind. 305, 380 N.E.2d 548; Frasier v. State, (1977) 267 Ind. 24, 366 N.E.2d 1166; Ind.R.P.C. 1, § 8. The trial court did not err in granting the State’s motion to strike those parts of the petition.
Appellant contends these issues form the underlying basis for his further allegations of inadequate representation by counsel, newly discovered evidence, and the State’s failure to disclose exculpatory evidence.
This Court has held the proper test of adequacy of representation by counsel, taking a totality of the circumstances approach, is the “mockery of justice” standard, as modified by the “adequate legal representation” standard. Hollon v. State, (1980) Ind., 398 N.E.2d 1273; Line v. State, (1979) Ind., 397 N.E.2d 975; Crisp v. State, (1979) Ind., 394 N.E.2d 115. The record in this case shows the conduct of a vigorous defense rather than a lack of knowledge or understanding of the law on the part of counsel. (See the original appeal of appellant’s conviction, Adams v. State, supra.)
Appellant claims he must use the errors committed at his trial as a basis for his post-conviction remedy arguments concerning newly discovered evidence and the State’s failure to disclose exculpatory evidence. We do not agree. Appellant is quite able to make his arguments regarding newly discovered evidence or the State’s failure to disclose exculpatory evidence without reference to the trial court’s alleged erroneous rulings.
Appellant claims the trial court erred in concluding appellant did not meet his burden of proof as to newly discovered evidence. The newly discovered evidence offered at the post-conviction proceeding was testimony from Viola Richards, appellant’s landlady who lived next door to appellant at the time of the crime, and Paula Vails, appellant’s girlfriend at the time of the robbery. Mrs. Richards testified she saw the co-defendant and another man, Jim Taylor, who was also a witness at the trial, exchange guns on the front porch of appellant’s home a few days before the crime. She also testified on the day of the robbery she saw Taylor and the co-defendant leave appellant’s home (the co-defendant roomed with appellant at the time) at about 10:30 A.M. on the day of the crime. The crime occurred about 11:00 A.M. Mrs. Richards testified she gave appellant’s counsel this information before the trial and though he said he would call her as a witness he never did.
Paula Vails testified appellant spent the night before the robbery with her at her home and did not leave the residence until about 11:00 A.M. that day in order to meet the co-defendant at a bar. She testified she gave appellant’s attorney this information and though he told her he would call her as a witness at the trial he did not do so.
P.C.R. 1(a)(4) provides a claim for post-conviction relief may be premised on “evidence of material facts, not previously presented and heard, that requires vacation of the conviction or sentence in the interest of justice . ... ” In interpreting this part *774of the rule, this Court has established several criteria that must be met before we will reverse the lower court’s denial of the petition. Among these is the petitioner must establish the evidence has been discovered since the trial. Clark v. State, (1978) 269 Ind. 90, 378 N.E.2d 850; Baker v. State, (1976) 265 Ind. 411, 355 N.E.2d 251; Torrence v. State, (1975) 263 Ind. 202, 328 N.E.2d 214. In the case at bar in presenting his argument of incompetency of counsel, appellant asserts the attorney was aware of the existence of this evidence. He, therefore, cannot for purposes of this allegation deny that assertion.
In order to be successful in a post-conviction relief petition, it must be shown the newly discovered evidence will probably produce a different result on retrial. Clark, supra; Baker, supra; Torrence, supra. In making this determination the post-conviction court “should consider the weight which a reasonable trier of fact would give the proffered evidence and the probable impact of it in light of all the facts and circumstances shown at the original trial of the case.” Torrence, supra, at 206, 328 N.E.2d at 217.
Given these guidelines, it is unlikely this evidence would produce a new result at retrial. The essence of the State’s evidence against appellant was his confession of a role in the crime to several of his acquaintances who were called as witnesses at the trial. In fact, there was evidence at the post-conviction proceeding appellant made such an admission to Mrs. Richards, though she denied that. Mrs. Richards was subpoenaed to appear as a witness by the State but did not appear. Her testimony does nothing to contradict the evidence that appellant confessed to the crime to several others and does nothing to establish appellant’s whereabouts at the time of the crime.
Thus, the post-conviction court had two bases for holding appellant failed to meet his burden of proof with respect to the newly discovered evidence argument: (1) the evidence was not newly discovered; and (2) on retrial it would not be likely to produce a different result. The trial court did not err concerning the “newly discovered evidence.”
Appellant next claims the trial court erred in denying relief on his allegation that his representation by counsel was inadequate. Appellant claims there was insufficient contact between he and his attorney prior to trial; that his attorney failed to call Viola Richards and Paula Vails as witnesses; that he failed to interview witness Jim Taylor prior to trial; that he refused to allow appellant to testify; failed to disclose witness Royce Richey’s “mental condition”; and failed to talk to the co-defendant.
The rule applied in determining adequacy of representation has been set forth earlier in this opinion. See, Hollon, supra; Line, supra; Crisp, supra. There is a strong presumption of the effectiveness of counsel that is overcome only by the presentation of convincing evidence to the contrary. Id.
Appellant and members of his family and acquaintances testified repeatedly they had trouble getting in touch with the attorney. Appellant stated he met with the attorney only twice prior to trial and that one of those times was on the first morning of the trial itself. On the other hand, the attorney for the co-defendant testified he worked closely with appellant’s attorney and knew the attorney visited Fort Wayne and talked with appellant at least six times after appellant was transferred to the jail there. Also, a Marion County sheriff produced records indicating the attorney visited appellant three times while he was still incarcerated there.
In post-conviction proceedings, the judge is the sole judge of the weight of the evidence and the credibility of witnesses. His decision is to be reversed only where the evidence is without conflict and leads unerringly to a result not reached by the trial court. Dobeski v. State, (1981) Ind., 419 N.E.2d 753; Lagenour v. State, (1980) Ind., 414 N.E.2d 295; Laird v. State, (1979) Ind., 385 N.E.2d 452. It is apparent the post-conviction judge chose to believe one set of witnesses and not the other. It is *775within his discretion to do so. We will not reverse that decision.
As to the allegation of failure to obtain separate trials, we note the evidence as to whether such a request was ever made is in conflict. Appellant testified he made such a request; however, the co-defendant’s attorney testified no such request was ever made. The rule cited above applies. The trial court’s finding is supported by evidence and will not be distrubed by this Court.
The attorney’s testimony also indicated the decision to move forward with joint rather than separate trials was a strategic one. We do not second-guess matters of trial strategy and tactics in evaluating an allegation of incompetence of counsel. Line, supra; Keys v. State, (1979) Ind., 390 N.E.2d 148.
As to the failure to call Viola Richards as a witness, the record shows the State had already subpoenaed her as a witness; however, she did not respond to that subpoena. Further, as above pointed out, the record demonstrates there was little or no value to the defendant as to Viola Richards’s testimony.
As to Paula Vails, the co-defendant’s attorney testified he had worked closely with appellant’s attorney at all stages of the pretrial and trial proceedings and had never heard Paula Vails’s name mentioned by anyone. Vails testified to the contrary to the effect she told appellant’s attorney of the alibi she had for appellant. As we have previously noted it is within the post-conviction judge’s discretion to weigh evidence and judge the credibility of witnesses. Dobeski, supra; Lagenour, supra; Laird, supra. Clearly a finding that appellant’s counsel did not demonstrate incompetence by failing to call Vails as a witness is supported by the testimony in this case. The trial court did not err in this regard.
As to witness Taylor, appellant does not make it clear what effect a pretrial interview would have had on the trial. The record also shows a vigorous cross-examination of Taylor was conducted. There is nothing in this record to disclose what an interview of him prior to trial would have accomplished. As to the decision to allow the co-defendant to take the witness stand but to have defendant exercise his right not to testify was purely a matter of trial tactics agreed upon by the attorneys representing the defendants. There is no demonstration whatever of any incompetence involved in this decision.
As to witness, Royce Richey’s, “mental condition” which appellant asserts should have been disclosed by his attorney, there is nothing in appellant’s brief which provides us guidance as to what this alleged “mental condition” was. We, therefore, deem this argument waived under Rule 8.3(A)(7) of the Indiana Rules of Appellate Procedure.
We find the trial court was correct in its finding appellant failed to meet his burden of proof in overcoming the strong presumption of the adequacy of representation.
Other errors of counsel appellant asserts illustrate inadequacy of representation are deemed waived by appellant’s failure to comply with Ind.R.App.P. 8.3(A)(7), which sets out the requirements for properly developing one’s argument with respect to issues presented for review. Appellant fails to develop a discernible argument with respect to allegations counsel demonstrated incompetence with regard to a conflict of interest or that he did so by failing to challenge the credibility of a State’s informant.
Appellant claims the trial court erred in finding he did not carry his burden of proof with respect to an alleged failure of the State to disclose exculpatory evidence, citing United States v. Agurs, (1976) 427 U.S. 97, 96 S.Ct. 2392, 49 L.Ed.2d 342. The gist of appellant’s allegation is the State had taken statements from Viola Richards that she had seen the co-defendant and Jim Taylor leaving appellant’s house together at about 10:30 A.M. on the morning of the crime (which was committed at around 11:00 A.M.), and that the State failed to disclose these statements to appellant.
*776Appellant’s argument on this point fails, as we do not see how this evidence is of such a nature as to fall within the rule. As we stated in State v. Wright, (1978) 267 Ind. 590, 593, 372 N.E.2d 453, 455, “[T]he ultimate issue is whether the prosecutor’s omission is of sufficient significance to result in a denial of the defendant’s right to a fair trial.” (Emphasis in original.) This evidence does not meet the test. The Supreme Court stated in Agurs, supra; “The mere possibility that an item of undisclosed information might have helped the defense, or might have affected the outcome of the trial, does not establish ‘materiality’ in the constitutional sense.” 427 U.S. at 109-110, 96 S.Ct. at 2400, 49 L.Ed.2d at 353. The most that can be said here is Richards’s testimony might have helped the defense by showing the co-defendant was with someone else half an hour before the robbery. Such testimony hardly excludes appellant from the scene of the robbery.
Further, it is hard to understand how appellant characterizes this as “undisclosed” evidence. Richards testified she spoke to appellant’s attorney by telephone prior to trial and told him exactly the nature of the testimony she wished to offer. Thus, the evidence was in fact disclosed to appellant through his counsel. The State was under no obligation to disclose what appellant already knew.
The post-conviction court is in all things affirmed.
DeBRULER, PRENTICE and PIVAR-NIK, JJ., concur. HUNTER, J., dissents with separate opinion.