Appellant was convicted of aggravated assault and battery in violation of § 6-2-502, W.S.1977 (Cum.Supp.1987). Imposition of sentence was delayed under § 7-13-203, W.S.1977, and appellant was placed on probation subject to several conditions, one being that he serve six months in the county jail. On appeal, he contends that he did not receive effective assistance of counsel and that the trial court erred by imposing a jail term as a condition of his delayed sentence.
We affirm appellant’s conviction and modify his sentence.
On July 26,1985, Officer James Jongsma of the Casper Police Department stopped a brown Mercedes for a license plate violation. The Mercedes was driven by appellant’s brother, Robert Laing. After discovering that Mr. Laing possessed neither a driver’s license nor any evidence of ownership of the car, Officer Jongsma asked him to get into the back seat of the police car. The officer then ran a check on the license plate and found that it was registered to another person and a different vehicle. The officer told Mr. Laing that he was going to take the rear license plate from the Mercedes. The officer unsuccessfully tried to remove the license plate by hand and then returned to his patrol car to get a pocket knife. He partially opened the patrol car door and, while leaning across the seat to get the knife, looked in his rear view mirror and saw appellant’s dark brown pickup truck approaching. Officer Jongsma testified that he
“recognized the truck from an earlier stop, recognized the driver of the truck, and saw the truck make a move or cor*1248rection, it veered slightly, as if it was lining up and the thing that registered on my mind was I know the truck, I know it is Tony Laing, and I saw him move, I thought he is lining up to hit me, and I then dove into the car in order to get out of his way.”
Officer Jongsma further testified that he saw a “determined look” on appellant’s face as he approached. Appellant’s truck hit the door of the police car and twisted it. After the accident, appellant told the officer that he was looking in the back of his truck at his dogs when the collision occurred. He also told the officer that he should not park with his door open. Officer Jongsma then arrested appellant.
The officer testified that he recognized appellant and his truck from an earlier incident when he had stopped appellant and cited him for having no registration and no driver’s license. He recalled that during the traffic stop, appellant had told him that he could “make more trouble for me than I would ever know what to do with.”
After the collision, appellant was interviewed by Officer James Cooper and signed a statement prepared by the officer. In the statement, appellant indicated that he had passed the police car on the other side of the road; he noticed that his brother had been pulled over; he turned around; as he approached the police car, the driver’s door was partially open and he could see the officer leaning “inside the squad car driver’s door”; the door then opened all the way and he hit it. The statement did not mention that appellant had been looking at his dogs when he struck the door.
Appellant was charged with aggravated assault and battery. Section 6-2-502, W.S. 1977 (Cum.Supp.1987) He pled not guilty and requested a jury trial. At trial, the prosecution presented the testimony of three police officers and appellant’s brother. The prosecution also introduced appellant’s statement into evidence. In presenting appellant’s defense, his attorney called two witnesses. One was appellant’s brother. The other was a land surveyor who testified concerning the width of the road where the collision occurred. The jury found appellant guilty as charged.
Appellant then appealed to this court, contending that his retained counsel rendered ineffective assistance because he failed to call appellant and two other witnesses to testify in appellant’s defense. We remanded the case to the district court for an evidentiary hearing on appellant’s claim of ineffective assistance of counsel. At the hearing, one of the witnesses not called at the trial, Rodney Hill, said that he would have testified at trial that he was present when appellant had allegedly threatened Officer Jongsma and that no threat was, in fact, ever made. The second witness not called at trial, Eric Olsen, said that he was an eye witness to the collision. He would have testified, contrary to Officer Jongsma’s version of the incident, that just before the collision, the patrol car door swung to its fully-open position. He also would have testified that there was a station wagon coming from the other direction which would have precluded appellant from going into the opposite lane to avoid hitting the door. Appellant contends that the testimony of these witnesses, if believed, would not only have impeached the State’s witness but “would have entirely exculpated appellant.”
When evaluating claims of ineffective assistance of counsel, we use a standard of reasonableness. Frias v. State, Wyo., 722 P.2d 135 (1986); Munden v. State, Wyo., 698 P.2d 621 (1985). We apply this standard of reasonableness within the framework of the bipartite test articulated in Strickland v. Washington, 466 U.S. 668, 104 S.Ct. 2052, 80 L.Ed.2d 674, reh. denied 467 U.S. 1267, 104 S.Ct. 3562, 82 L.Ed.2d 864 (1984); Frias v. State, supra. The Strickland standard requires appellant to demonstrate that the performance of his attorney was deficient and that the deficiency prejudiced the defense of the case. Gist v. State, Wyo., 737 P.2d 336 (1987).
In order to satisfy the first prong of the Strickland test, deficient performance of counsel, appellant must show that his attorney was not functioning as the “counsel” guaranteed by the Sixth Amendment to the *1249United States Constitution. Id. We conclude that appellant has failed to make this showing. In Strickland, the United States Supreme Court stated that when analyzing a claim of deficient performance,
“[¡judicial scrutiny of counsel’s performance must be highly deferential. It is all too tempting for a defendant to second-guess counsel’s assistance after conviction or adverse sentence, and it is all too easy for a court, examining counsel’s defense after it has proved unsuccessful, to conclude that a particular act or omission of counsel was unreasonable. Cf. Engle v. Isaac, 456 U.S. 107, 133-134, 102 S.Ct. 1558, 1574-1575, 71 L.Ed.2d 783 (1982). A fair assessment of attorney performance requires that every effort be made to eliminate the distorting effects of hindsight, to reconstruct the circumstances of counsel’s challenged conduct, and to evaluate the conduct from counsel’s perspective at the time. Because of the difficulties inherent in making the evaluation, a court must indulge a strong presumption that counsel’s conduct falls within the wide range of reasonable professional assistance; that is, the defendant must overcome the presumption that, under the circumstances, the challenged action ‘might be considered sound trial strategy.' See Michel v. Louisiana, supra, 350 U.S., [91] at 101, 76 S.Ct., [158] at 164 [100 L.Ed. 83 (1955)]. There are countless ways to provide effective assistance in any given case. Even the best criminal defense attorneys would not defend a particular client in the same way.
* * * * *
“Thus, a court deciding an actual ineffectiveness claim must judge the reasonableness of counsel’s challenged conduct on the facts of the particular case, viewed as of the time of counsel’s conduct. A convicted defendant making a claim of ineffective assistance must identify the acts or omissions of counsel that are alleged not to have been the result of reasonable professional judgment. The court must then determine whether, in light of all the circumstances, the identified acts or omissions were outside the wide range of professionally competent assistance. In making that determination, the court should keep in mind that counsel’s function, as elaborated in prevailing professional norms, is to make the adversarial testing process work in the particular case. At the same time, the court should recognize that counsel is strongly presumed to have rendered adequate assistance and made all significant decisions in the exercise of reasonable professional judgment.” Strickland v. Washington, supra, 104 S.Ct. at 2065-2066.
The Strickland court went on to say that “strategic choices made after thorough investigation of law and facts relevant to plausible options are virtually unchallengeable.” Id., 104 S.Ct. at 2066. In Gist v. State, supra, we noted that we support “the general proposition that a decision as to whether to call a particular witness is a matter of trial tactics properly committed to the discretion of counsel.” Id., 737 P.2d at 343.
It is clear that in this case the purported deficiencies in counsel’s performance are not the result of inadequate investigation or preparation; instead, they fall into the “virtually unchallengeable” category of “strategic choices made after thorough investigation.” Strickland v. Washington, supra, 104 S.Ct. at 2066. Cf. Frias v. State, supra; Gist v. State, supra. Appellant’s trial counsel testified that he did not call appellant to the stand because he thought that he would not be a good witness and he thought that appellant’s statement, which was introduced into evidence, adequately presented appellant’s version of the incident. He did not call Rodney Hill as a witness because after two or three interviews, he was not sure whether Mr. Hill would testify that he had heard the entire conversation between Officer Jongs-ma and appellant when appellant allegedly threatened the officer. In addition, Mr. Hill was a good friend of appellant’s. Mr. Olsen was not called because his description of the incident when interviewed before trial was not as vivid as his description *1250in the evidentiary hearing on remand. (It is an unexplained phenomenon that often, after conclusion of a trial and with passage of time, a witness’ description of an incident becomes more colorful and detailed or certain.) Given these circumstances, we cannot say that the decision to refrain from calling the witnesses was unreasonable or “outside the wide range of professionally competent assistance.” Strickland v. Washington, supra, 104 S.Ct. at 2066. We reject appellant’s claim of ineffective assistance of counsel.
Turning to appellant’s second issue, we agree that the trial court erred in requiring appellant to spend six months in the county jail as a condition to a delayed sentence. In pertinent part, § 7-13-203, W.S.1977, provides:
“If the court is satisfied that he was a person of good reputation before the commission of the offense charged and had never before been convicted of any felony, and that if permitted to go at large would not again violate the law, the court may in its discretion, by an order entered of record, delay passing sentence and then parole the person and permit him to go at large upon his own recognizance, conditioned that he will personally appear and report to the court twice in each year at times and places fixed in the order and that he will demean himself while at large in a law-abiding manner and live a worthy, respectable life, and that he will not leave the state without the consent of the court.”
In sentencing appellant, the trial court concluded that “the passing of sentence herein should be delayed pursuant to W.S.1977, § 7-13-203” and ordered that appellant be placed upon supervised probation1 for a period of not less than one year nor more than five years subject to the condition, among others, that he be “remanded to the custody of the Natrona County Sheriff’s office to serve a term of six (6) months.”
In Sorenson v. State, Wyo., 604 P.2d 1031 (1979), we said that “[t]here can be no incarceration in connection with the status of the defendant under [§ 7-13-203].” Id. at 1038, n. 6. In light of this statement, the State understandably concedes that § 7-13-203 does not allow incarceration as a condition of a delayed sentence.
If part of a divisible sentence is illegal or improper, we may modify it by vacating or striking that part which is illegal and improper and affirm the balance. Sorenson v. State, supra. Accordingly, we strike the requirement of six months incarceration.
Appellant’s conviction is affirmed, and his sentence is affirmed as modified.
CARDINE, J., delivered the opinion of the court.
URBIGKIT, J., filed a dissenting opinion in which MACY, J., joined.
. In Sorenson v. State, Wyo., 604 P.2d 1031 (1979), we observed that the proper status of a defendant under § 7-13-203, W.S.1977, is “probation" rather than "parole.”