Defendant Fred Dale LeFever asks this court to reverse a decision of the Court of Appeals which affirmed his conviction of one count of first degree robbery and two counts of second degree robbery, a finding of his being a habitual criminal, and ruled his probation was properly revoked.
The charges against defendant arose out of three robberies at two Safeway stores in Seattle which occurred on September 5 and 7, and October 17, 1981. In each robbery the robber disguised himself by putting Band-Aids on his face, stuffing cotton up his nostrils, and wearing a fake beard and sideburns.
Defendant was arrested on October 20, 1981. His parole officer, James Kairoff, was present. Defendant asked to speak with him. Although Kairoff told defendant he had no obligation to say anything, defendant chose to tell Kairoff he had a $125-a-day heroin habit and that he had made arrangements to enroll in a drug rehabilitation program the next day. Defendant told Kairoff his wife was providing him with enough money to buy heroin during the 5-day waiting period prior to entry into the drug program. At the *780time, defendant was earning $1,400 per month and his wife's earnings totaled $320 per month.
At trial, the court ruled defendant's admissions of heroin addiction to Kairoff were not privileged, but were admissible to show motive to commit the robberies.
Before trial, the State moved to use prior convictions against defendant to prove identity. ER 404(b). This the trial court denied. Defendant's counsel then moved to exclude from evidence defendant's 1974 conviction of three counts of robbery for impeachment purposes. Counsel suggested defendant could instead be impeached with his 1971 forgery conviction or 1980 theft conviction, or that the 1974 convictions could be used without specifying their nature. This motion was also denied and the court ruled all prior convictions could be used for purposes of impeachment.
At trial, defendant attempted to introduce the testimony of Robert Boruchowitz, Director of the Public Defender's Office for King County. During an offer of proof, Borucho-witz testified he routinely attends lineups to advise suspects and interview witnesses and make written records of the relative certainty of witnesses' identifications. His notes for October 21, 1981, indicated some of the State's witnesses' identifications of defendant in the lineup had been tentative. When questioned, however, Boruchowitz was unable to state the exact source of his information. This testimony was ruled inadmissible.
Defendant did not testify at trial. He was convicted of all three robberies. In his motion for a new trial, defendant submitted an affidavit which states he did not testify because of the danger of unfair prejudice he feared would result from cross examination regarding prior convictions. Additionally, he was concerned "the evidence of his heroin use created an issue which was not relevant to the charges against him and which unfairly influenced the jury to convict him." If allowed to testify, defendant would have alleged he began using heroin approximately 3 weeks before his arrest, his drug use had initially cost only $20 per day, he occasionally obtained heroin by selling drugs to others, *781and he had used a $600 settlement for collision damage to his car to buy heroin. This testimony would support defendant's claim that the funds used to purchase heroin were from sources other than the proceeds of the robberies. The motion for new trial was denied.
Subsequently, defendant was charged with being a habitual criminal. Four prior convictions were alleged: (1) 1971 conviction for first degree forgery; (2) 1972 federal conviction for possession with intent to distribute heroin; (3) 1974 conviction for three counts of robbery; and (4) 1980 conviction for possession of stolen property in the second degree. Counsel for the defendant challenged the 1980 conviction which was then on appeal and argued the other three convictions could not be used because they were based on constitutionally invalid guilty pleas. The court initially granted the motion to dismiss the habitual criminal proceeding, finding the 1980 conviction could not be used because it was on appeal and the 1974 convictions to be based on constitutionally infirm guilty pleas.
A subsequent motion by the State for reconsideration was granted, the court stating it had "granted the motion to dismiss on the mistaken interpretation of fact that there were only four convictions before the Court whereas there apparently were five, the instant one and four previous." Moreover, in the previous hearing, the court had not ruled on the 1971 and 1972 convictions. The court went on to find the 1971 and 1972 convictions constitutionally valid and defendant guilty of being a habitual criminal.
Thereafter, defendant was given notice of a probation revocation hearing based on his robbery convictions in 1982 and his habitual criminal status. In June 1982 an order was entered revoking defendant's probation on his 1980 conviction for possession of stolen property. During oral argument, the parties agreed this decision was based solely upon defendant's convictions of robbery and of being a habitual criminal and not his addiction to heroin.
The Court of Appeals affirmed all lower court proceedings, State v. LeFever, 35 Wn. App. 729, 669 P.2d 1251 *782(1983). We granted defendant's petition for review.
I
Defendant argues it was error to admit evidence of his heroin addiction as proof of motive for the robberies. He believes this evidence was impermissible under ER 404(a) as it was used to show his character "for the purpose of proving that he acted in conformity therewith . . ." Additionally, defendant contends any probative value of this evidence was substantially outweighed by the danger of undue prejudice. ER 403. The State argues the heroin addiction evidence was significant to show defendant's financial need to support his habit which was relevant to explain his motive and therefore admissible under ER 404(b). Moreover, the State asserts the trial court carefully balanced the probative as opposed to the prejudicial effect of the evidence and thereafter properly admitted the evidence.
The admissibility of evidence of an illegal drug addiction to prove motive is governed by ER 404(b).
Evidence of other crimes, wrongs, or acts is not admissible to prove the character of a person in order to show that he acted in conformity therewith. It may, however, be admissible for other purposes, such as proof of motive
This rule must not be read in a vacuum but in conjunction with ER 401 through 403. State v. Saltarelli, 98 Wn.2d 358, 361-62, 655 P.2d 697 (1982). Thus, motive evidence is admissible only if it is relevant, making the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence. ER 401, 402. If relevant, then the probative value of the evidence must be balanced against its prejudicial effect. ER 403. Regardless of whether the evidence is relevant or probative, in no case may evidence be admitted to prove the character of the accused in order to show that he acted in conformity therewith. ER 404(b); State v. Saltarelli, supra at 362.
*783The Court of Appeals found defendant's addiction was highly probative of motive — there was conclusive evidence of a costly habit, he did not have sufficient legitimate income to finance his addiction, and the physical and mental suffering associated with heroin addiction provided a compelling impetus to resort to illegal means. 35 Wn. App. at 733. Although noting evidence of drug use may have some prejudicial effect, the Court of Appeals ruled the trial court cautiously treated any prejudicial effects and did not abuse its discretion in admitting evidence.
Other courts faced with this issue have split over the admissibility of evidence of a defendant's drug addiction. Annot., Admissibility of Evidence of Accused's Drug Addiction or Use To Show Motive for Theft of Property Other Than Drugs, 2 A.L.R.4th 1298 (1980). The two cases most factually similar to this appeal are People v. Cardenas, 31 Cal. 3d 897, 647 P.2d 569, 184 Cal. Rptr. 165 (1982) and Gould v. State, 579 P.2d 535 (Alaska 1978). Those cases and this appeal both involve convictions based upon inconsistent eyewitness testimony.
In Cardenas, defendant was convicted of attempted murder and robbery and assault with a deadly weapon. The prosecution's case, however, was not overwhelming. 31 Cal. 3d at 907. First, the witnesses' estimates of the assailant's height (5 feet 7 inches to 5 feet 9 inches) did not approximate the height listed for defendant when booked (5 feet 2 inches). Second, two witnesses indicated he was clean shaven, while a third thought he wore a moustache and beard. Third, not a single witness was able to identify the defendant consistently in mug shots and a pretrial lineup. 31 Cal. 3d at 908. The court was bothered by the closeness of the case and the fact defendant's heroin addiction was mentioned eight separate times. 31 Cal. 3d at 909. In reversing the conviction the court recognized:
The impact of narcotics addiction evidence "upon a jury of laymen [is] catastrophic. ... It cannot be doubted that the public generally is influenced with the seriousness of the narcotics problem . . . and has been *784taught to loathe those who have anything to do with illegal narcotics . . .
31 Cal. 3d at 907 (quoting People v. Davis, 233 Cal. App. 2d 156, 161, 43 Cal. Rptr. 357 (1965)). See, e.g., State v. Ren-neberg, 83 Wn.2d 735, 737, 522 P.2d 835 (1974) ("evidence of drug addiction is necessarily prejudicial in the minds of the average juror").
In Gould, the four eyewitnesses described the defendant as having a moustache. Four defense witnesses testified, however, that the defendant had a full beard on the day of the robbery. The Supreme Court of Alaska held it was error to admit evidence of defendant's heroin habit due to the
absence of any "affirmative link" between the robbery and Gould's alleged heroin addiction. The only possible relevance of this evidence goes to the hotly contested issue of identification. The state's argument for relevance is based on reasoning that because Gould was unemployed and had a $300 a day heroin habit, he had to commit the robbery to support his habit. . . . [W]e find the proffered inference too attenuated and possessing "too many gaps" to show motive and thus the identity of the robber.
579 P.2d at 539. See also Christian v. Tuscaloosa, 53 Ala. App. 81, 297 So. 2d 405 (1974); State v. Sutfield, 354 So. 2d 1334 (La. 1978); Jones v. State, 38 Md. App. 432, 381 A.2d 317 (1978); Powell v. State, 478 S.W.2d 95 (Tex. Crim. App. 1972). Contra, United States v. Saniti, 604 F.2d 603 (9th Cir.), cert. denied, 444 U.S. 969 (1979); United States v. Parker, 549 F.2d 1217 (9th Cir.), cert. denied, 430 U.S. 971 (1977); Archie v. State, 137 Ga. App. 386, 224 S.E.2d 64 (1976); People v. McConnell, 124 Mich. App. 672, 335 N.W.2d 226 (1983).
We concur in the views expressed by the California and Alaska courts in their refusal to admit evidence of heroin addiction to show a link between the robberies and the addictions where the issue was identification. In this case we, too, are troubled by the wide variances in eyewitness testimony. Defendant's witnesses testified LeFever had a prominent moustache when the robberies occurred. Because *785of the robber's disguises, however, some eyewitnesses to the crime remembered the robber with a moustache, while others did not. Even if the heroin habit could be used to show motive, where identification is the key element to be proved, the fact that defendant was a heroin user had limited probative value to show that he committed the robberies. When, as here, identification is crucial and eyewitness testimony as to identity is confused at best, it is error for the prosecution to introduce evidence of defendant's addiction to heroin. The resultant prejudice to one accused of a crime completely overwhelms any possible relevance or probativeness.
The trial court erred in allowing the State to introduce evidence of LeFever's heroin addiction as proof of motive for the robberies. Within reasonable probabilities, we find had the error not occurred, the outcome of the trial would have been materially affected. State v. Robtoy, 98 Wn.2d 30, 44, 653 P.2d 284 (1982). We hold this error not to be harmless but to be prejudicial and grounds for reversal.
II
Defendant contends the trial court also erred by admitting evidence of his 1974 robbery convictions for purposes of impeachment. ER 609(a)(1). The Court of Appeals, finding defendant failed to make a timely offer of proof, did not reach the merits of this assertion. State v. LeFever, 35 Wn. App. 729, 736, 669 P.2d 1251 (1983) (quoting State v. Hebert, 33 Wn. App. 512, 516, 656 P.2d 1106 (1982)). Recently, in State v. Koloske, 100 Wn.2d 889, 676 P.2d 456 (1984), we ruled
if [a] defendant elects not to testify following a ruling under ER 609, defendant must ensure that the record includes a declaration of his intention to testify and an adequate offer of proof, either oral or written, to preserve any error for appellate review.
100 Wn.2d at 897. See State v. Pam, 98 Wn.2d 748, 763, 659 P.2d 454 (1983) (Utter, J., concurring).
*786In Koloske, we noted the trial court in most cases will find it necessary to evaluate the significance of defendant's testimony to the case before a proper ruling can be made. Moreover, we looked with disfavor upon defendants with no intention of testifying, who may seek a ruling in order to provide an additional ground for appeal in case of conviction, thereby potentially abusing ER 609. 100 Wn.2d at 897. Here, the defendant waited until his motion for a new trial to file an affidavit delineating his reasons for not testifying. Such a delay is too late to preserve his assignment of error.
We hold an offer of proof must be made, if a defendant elects not to testify, at the time of an ER 609 ruling. Only then may a court properly evaluate the importance of defendant's testimony and properly exercise its discretion through the balancing procedure prescribed by ER 609. State v. Alexis, 95 Wn.2d 15, 19, 621 P.2d 1269 (1980). This rule also enables the trial court to comply with the mandatory rule we set out in State v. Jones, 101 Wn.2d 113, 677 P.2d 131 (1984), which requires it to "state, for the record, the factors which favor admission or exclusion of prior conviction evidence." 101 Wn.2d at 122.
Not only did defendant fail to make a timely offer of proof, but the trial court also failed to delineate on the record its reasons for admitting the prior robbery convictions. These reasons, and the fact we are reversing on other grounds and cannot predict what motions and rulings will be made on any retrial, foreclose us from determining whether the trial court erred in admitting LeFever's prior convictions for impeachment purposes.
Ill
Defendant asserts the trial court erred in excluding the testimony of Boruchowitz regarding the tentative nature of lineup identifications made by certain State witnesses. The Court of Appeals affirmed the exclusion, finding an inadequate foundation for admissibility. 35 Wn. App. at 736.
The general rule is " [a] witness may not testify to a matter unless evidence is introduced sufficient to support a *787finding that he has personal knowledge of the matter." ER 602. The burden of laying a foundation that a witness had an adequate opportunity to observe the facts to which he testifies is upon the proponent. 5 K. Tegland, Wash. Prac., Evidence § 219 (2d ed. 1982).
Boruchowitz testified he obtained his information by observing the witnesses mark the identification form and by interviewing the witnesses and detectives present. He was completely unable to specify the exact source of his proposed testimony with respect to specific witnesses. The burden of introducing sufficient evidence to support a finding of personal knowledge was not met. We affirm the trial court's ruling that the testimony of Boruchowitz was inadmissible.
IV
Next, defendant contends the trial court's reconsideration and reversal of its decision dismissing his habitual criminal proceeding violates the double jeopardy clause of U.S. Const. amend. 5 and Const. art. 1, § 9. The Court of Appeals found no error and upheld the trial court's finding that LeFever was a habitual criminal. 35 Wn. App. at 740.
The trial court initially orally ruled "[o]n the basis of the argument and the briefs and a study of the cases, the Court grants the motion to dismiss the habitual criminal proceeding." The State contested this ruling but the court responded, "my rulings stand." Four days later, upon the State's motion for reconsideration, the trial court ruled on two other convictions it had not considered earlier and found the defendant to be a habitual criminal.
When a trial court dismisses a criminal case for insufficient evidence, no matter how erroneous that ruling may be, retrial of the defendant is precluded by the double jeopardy clause. The State may not obtain a motion to reconsider. State v. Dowling, 98 Wn.2d 542, 545, 656 P.2d 497 (1983).
A finding by the court as the trier of fact, without a jury, when read conclusively into the record in such a *788manner as to indicate that it is neither tentative nor made with reservation or advisement nor subject to further consideration or proceedings in the same case, will support a judgment of acquittal or dismissal.
98 Wn.2d at 547 (quoting State v. Bastinelli, 81 Wn.2d 947, 956, 506 P.2d 854 (1973)). We hold this same rule also applies to habitual criminal proceedings.
The record before us indicates the trial court's initial dismissal of the habitual criminal charge was a judgment of dismissal. It was not tentative nor subject to further consideration. Hence, the double jeopardy clause barred the subsequent proceeding in which defendant was found to be a habitual criminal. We reverse the finding of the trial court that defendant is a habitual criminal.
V
Lastly, defendant argues the trial court erred in revoking his probation. As noted previously, defendant's probation was revoked based upon his conviction of the robberies and of being a habitual criminal.
[I]f probation for an earlier conviction is revoked solely on the basis of a new conviction that we subsequently reverse and remand for a new trial, the trial court must hold a new probation revocation hearing.
State v. Dowell, 26 Wn. App. 629, 632, 613 P.2d 197 (1980). This procedure must be followed here.
Defendant's convictions of one count of first degree robbery and two counts of second degree robbery are reversed; the finding he is a habitual criminal is reversed; the case is remanded to the trial court for a new probation revocation hearing.
Williams, C.J., and Utter, Brachtenbach, Dore, and Pearson, JJ., concur.
Rosellini, J., and Cunningham, J. Pro Tern., concur in the result.