Defendant, Larry LeMasters, appeals a judgment and jury verdict finding him guilty of first degree burglary, second degree burglary, criminal attempt to commit aggravated robbery, second degree assault, and menacing. We affirm.
On a snowy day in November of 1980, the victim was interrupted by the doorbell while talking with a friend on the telephone. Before opening the door she asked the man outside what he wanted, and he explained that one of his co-workers had fallen from the scaffolding at a nearby construction site and he needed to call an ambulance. The victim let the man in, then hung up the phone, asking her friend to call back in two minutes.
The man explained that he needed to call the home office for authorization before sending for an ambulance. After dialing a few times he told the victim he was unable to get through. The man asked for a glass of water, which the victim provided. He replaced it in the sink and asked to use the restroom. While defendant was in the restroom, the victim became apprehensive and placed a kitchen knife on the counter next to her.
After making one more attempt at reaching the home office, the man turned and lunged at the victim with a knife. A struggle ensued during which the victim managed to activate a silent alarm. She told her attacker that he had better leave because the police would soon be coming. After the man demanded money, the victim reached for her purse and made a run for the garage. She was able to activate the automatic door opener and began screaming loudly. The man fled.
The victim reentered the house and attempted to call for help, but the line had been cut. She then ran into the street to flag down a van. The driver told her to get in and they followed the man’s car, as a result of which they were able to obtain the license number and the car’s description.
Defendant’s arrest and conviction followed. Defendant’s appeal is based on the contentions that evidence was improperly admitted and that he was denied his right to effective assistance of counsel. We affirm.
I.
Defendant first argues that a hood and sweater of his, which were suppressed as a result of an invalid search, were improperly *576introduced for impeachment purposes. We disagree.
Here, the trial court properly admitted pieces of defendant’s clothing which had been described by the victim to impeach the defendant’s testimony that he was not at the victim’s home on the day in question. The defense argues that because the defendant specifically admitted owning the articles of clothing, there was nothing to impeach.
In United States v. Havens, 446 U.S. 620, 100 S.Ct. 1912, 64 L.Ed.2d 559 (1980), the Supreme Court held that evidence suppressed as the fruit of an unlawful search and seizure may nevertheless be used to impeach a defendant’s false trial testimony, given in response to proper cross-examination, even where the evidence does not squarely contradict the defendant’s testimony on direct examination. It is not necessary that the matter be expressly mentioned on direct; rather, it is permissible to use the impeachment evidence if the direct examination suggests the question to a reasonably competent cross-examiner. This exception has been made because a court’s overriding concern is to arrive at the truth and not permit a defendant to base his case on perjured testimony.
The items were not offered to impeach a statement as to ownership. Rather, they were offered to impeach defendant’s statement that he was not at the victim’s house on the day of the crime. When asked on direct examination by his counsel, “Mr. LeMasters, on November 24, 1980, were you at the Weilly residence?” the defendant replied “No, I was not.” The trial court properly interpreted Havens to allow cross-examination regarding the clothing defendant was wearing on the day of the crime because it contradicted the alibi defense introduced during direct examination of defendant.
II.
Defendant next contends that evidence concerning two test drives used to corroborate distances between stops the defendant made on the morning of November 24, and the time necessary to drive those distances was improperly admitted.
The first test drive was conducted on February 27, 1981, in response to defendant’s written notice of alibi provided pursuant to Crim.P. 12.1. Defendant claims that because the roads were dry during the test drive, whereas on the day of the incident they were snowpacked, the test conditions were dissimilar and, thus, the test had no probative effect. However, the officer testified that he drove slowly to compensate for the difference in weather conditions on the two days.
Moreover, minor variations, such as weather conditions, have been held to affect only the weight but not the admissibility of similar tests. People v. McCombs, 629 P.2d 1088 (1981); People v. Sexton, 192 Colo. 81, 555 P.2d 1151 (1976). Whether or not test conditions are substantially similar to those being recreated is a matter for the trial court’s discretion, and any doubts concerning test reliability may be adequately explored on cross-examination. People v. Bastardo, 191 Colo. 521, 554 P.2d 297 (1976). Thus, we see no error in the trial court’s ruling.
The second test was performed because, during the trial, the defendant’s testimony was inconsistent with his previous written alibi statement as to the hours he claimed he spent at each location. Defendant contends that this second test drive was also inadmissible because the results of the drive were not provided in the normal course of discovery and that this violated the prosecution’s constitutional duty to disclose evidence under Brady v. Maryland, 373 U.S. 83, 83 S.Ct. 1194, 10 L.Ed.2d 215 (1963). We disagree.
First, it was not possible to provide defendant with the results of the second test drive in the normal course of discovery because it was performed during the trial itself. Moreover, defense counsel did not act properly to preserve defendant’s objection to the introduction of testimony regarding the test drive. The defense al*577lowed the testimony to be fully read into the record and made no contemporaneous objection. Only after the witness was through testifying did the defense make any sort of an objection at all, and it was in the form of a motion for a mistrial, which was denied. If defense counsel wished to examine the results of the second test drive, he need only have moved for a continuance. This he failed to do. Under these circumstances, we do not perceive a constitutional violation under Brady.
III.
Defendant’s third contention is that the prosecution did not establish a proper chain of custody for fingerprint evidence taken from the water glass in the victim’s house. We disagree.
The testimony of an officer in charge of the property room established where, and in whose custody, the prints were at all times. Defendant’s arguments, inter alia, that the envelope containing the prints was unsealed, constitute no more than mere speculation $s to tampering. Mere speculation is insufficient to establish a break in the chain of custody. People v. Gomez, 632 P.2d 586 (Colo.1981).
IV.
Defendant further claims that the fingerprints should not have been admitted because, once the prints were lifted, the glass was returned to the victim. Defendant claims that the returning of the glass to the victim destroyed the evidence, making it unavailable for him to conduct independent tests, and constituted a violation of due process under Garcia v. District Court, 197 Colo. 38, 589 P.2d 924 (1979). Not so.
Garcia provides a three-part test to determine whether a due process violation has occurred when evidence is lost or destroyed:
“(1) whether the evidence was suppressed or destroyed by the prosecution; (2) whether the evidence is exculpatory; and (3) whether the evidence is material to the defendant’s case.”
We hold that the first part of the Garcia test is not satisfied in this case because the evidence was not actually destroyed. Even though the glass was unavailable, the defendant had the opportunity to examine the prints themselves, and a court-appointed expert was provided for this purpose.
This case is not analogous to Garcia which involved the destruction of a breathalyzer sample taken to establish driving under the influence. Once the breath sample in Garcia was destroyed, the ability to conduct independent testing was also destroyed. Here, the defendant was still able to examine the actual prints as lifted from the glass.
Moreover, in Garcia, “the defendant ... presented competent evidence that a separate breath sample could have been independently tested and the results of that test used to ‘impeach’ the ‘testimony’ of the machine which tested his breath.” Here, although a fingerprint expert was provided to defendant, that expert did not testify concerning the feasibility of independent tests. The court, thus, had no way to determine whether a second set of prints could have been lifted from the glass and independently tested.
Further, the third prong of the Garcia test is also not satisfied in this case. The standard for determining materiality is whether the evidence could have affected the outcome at trial in light of the other evidence presented. People v. District Court, 656 P.2d 1287 (Colo.1983). See also People v. Shaw, 646 P.2d 375 (Colo.1982). We conclude that, in light of the other evidence presented at trial — photographic and in-court identifications of the defendant and his clothing, descriptions of the car and license plates, and inconsistent alibi stories — evidence gained from a second lifting of fingerprints would not have affected the outcome of the trial.
Defendant also argues that it was error for the trial court to allow the prosecution to offer a similar glass into evidence because under Hampton v. People, 171 Colo. 101, 465 P.2d 112 (1970), such *578evidence was highly prejudicial to the defendant. We find no merit in this argument. The prosecution used the glass simply to show the jury how a fingerprint expert lifts a print from such a surface. It is within the discretion of the trial court to admit models for purposes of demonstration. Hampton, supra. Moreover, defendant has established no prejudice resulting from the admission of the glass.
V.
Defendant’s final argument is that the failure of his prior counsel to interview alibi witnesses in a timely manner denied his right to effective assistance of counsel. Again we disagree. Ineffective assistance of counsel is not established merely through failure to interview potential alibi witnesses within two weeks after the preliminary hearing. See People v. Grant, 40 Colo.App. 46, 571 P.2d 1111 (1977) (failure to interview witnesses within 6 days after preliminary hearing not prejudicial).
Judgment affirmed.
STERNBERG, J., concurs and specially concurs. SMITH, J., dissents.