These appeals follow the convictions of Tracy and Joseph Watson for drug trafficking and conspiracy. A jury convicted Tracy of one count of conspiring to possess cocaine with intent to distribute in violation of 21 U.S.C. § 841(a)(1) and 846 (1988); Tracy also was found guilty of nine counts of distributing cocaine and cocaine base in violation of 21 U.S.C. § 841(a)(1). Joseph was convicted of the same conspiracy charge and found guilty of six counts of distributing cocaine and cocaine base. The brothers claim the District Court 1 erroneously refused to compel the prosecutor to testify about prior conversations with the government’s witness; they also claim that the introduction of an informant’s hearsay statements violated their rights under the Sixth Amendment to the federal Constitution. Tracy Watson also asks us to review the sufficiency of the evidence presented against him and to correct an alleged error in his sentence. We affirm.
I
The St. Louis police began to investigate the activities of Tracy and Joseph after an informant claimed they were selling drugs from some local apartments. In April 1990, Detective Richie Williams resolved to visit that area equipped with a concealed radio transmitter whose signals were to be *984 recorded in a nearby surveillance vehicle. Williams employed this apparatus to record all the transactions he made with the defendants over the following two months. He first went to the locality on April 19, 1990. When he arrived, an unidentified man approached him and asked if he wanted to buy cocaine. Williams said he did and asked after “Tracy.” The unidentified man then summoned Tracy Watson, who instructed Williams to park his vehicle. Once this had been done, Tracy entered the vehicle and displayed what Williams later recalled was a “clear bag that containеd a very large amount of off-white chunks,” which Williams “believed to be [cocaine base].” Trial Transcript (hereinafter “Tr.”) at 16. Williams purchased five pieces for $100.
When the Detective returned on April 23, Tracy said he was out of cocaine but that he would soon have additional merchandise. Williams returned an hour later. Upon seeing him, an unidentified man went inside a nearby apartment and emerged with instructions for Williams to enter. Williams complied, and upon entering met Tracy. After discussing the provenance of cocaine and its price, Williams bought ten pieces of cocaine base frоm Tracy for $200. Five days later, Williams and Tracy discussed future drug deals and the detective spent $200 to purchase another nine pieces of cocaine base.
On April 26, 1990, Williams met Tracy in one of the apartments and offered to buy twenty pieces of cocaine base. From under a chair cushion, Tracy removed a plastic bag containing cocaine and directed Williams to follow him into the rear bedroom. Once inside, Tracy removed the bag’s contents and discovered he did not have the amount Williams wanted. According to Williams, Tracy “then called for his brother to bring him more cocaine.” Joseph entered the room and removed a bag from his pocket, and Tracy told him to close the door. Tracy took eight pieces of cocaine base from his own bag, and Joseph removed twelve from the bag he had brought into the room. Williams then gave Tracy $400, which the defendant split between himself and Joseph.
Williams returned to the area on the following afternoon and was approached by an unidentified male who asked if he had come to buy cocaine. When Williams said he had, this person called for Tracy, who sold Williams sixteen pieces of cocaine base for $360. Tracy also gave Williams an additional piece free of charge; as Williams later recalled, this was “for being a good customer.” Tr. at 42. During this transaction Williams talked to Tracy about buying a large amount of cocaine.
On April 30 Williams saw Tracy outside one apartment with a group of men, one of whom hailed the Detective as “the $400 man.” Tr. at 46. Tracy proclaimed to all present that he knew who his regular customers were and invited Williams into the apartment. Once inside, Tracy said he had been unable to get a large amount of cocaine, but that he could рrobably acquire it by the week’s end. Williams told Tracy he intended to sell cocaine in Springfield because it was a good market. Tracy said he had heard the same thing about Springfield: “My partner be down there. He was tellin’ me ‘bout that.” Government’s Exhibit 6. Williams bought twenty pieces of cocaine base from Tracy for $400. During this transaction Tracy said he would be leaving St. Louis to obtain more cocaine in preparation for the first of the month, because he could earn approximately $12,000 on the day welfare checks were issued.
On May 2, 1990, Tracy told Williams that he was not selling cocaine anymore, but sent the Detective to Joseph as a possible supplier. Williams offered to buy an ounce of cocaine from Joseph, who said he would try to obtain that amount. Joseph then agreed to sell Williams twenty pieces of cocaine base for $400 and to give Williams one free portion. Upon finding he only had nineteen pieces, Joseph instructed a man named “Tim Tim” to watch the cocaine while he left the room. Joseph returned with a bag containing approximately thirty pieces of cocaine base, two of which he selected to make up the amount.
On May 4,1990, Williаms was directed to Joseph by a minor. Williams met with *985 Joseph, Tracy, and a third person. Tracy repeated that he was not selling cocaine anymore, but again referred Williams to his brother. Joseph ultimately sold Williams thirty-three pieces of cocaine base for $660. During this time the Detective and Joseph discussed the possible sale of an ounce of cocaine, and discussed the lookouts Joseph used to safeguard his business.
When Williams returned on May 8, 1990, an unidentified man told him Joseph was not selling cocaine base, but that he was selling powdered cocaine. When Williams spoke with Joseph, the defendant said his supplier would not agree to provide an ounce of cocaine. Williams bought seventeen bags of powdered cocaine. Ten bags were supplied by Joseph, and Tracy provided seven bags to complete the amount. Williams then paid Joseph $850.
On May 9, 1990, Williams again spoke to Joseph about buying an ounce of cocaine. Joseph said he did not think he could provide this amount, but that he would try. Joseph offered to sell Williams seventeen bags of powdered cocaine at $50 each, and to provide two free bags. When Williams agreed, Joseph left and entered a nearby apartment. A short time later, Tracy emerged from this apartment and told Williams to enter another apartment. Once inside, Tracy began to measure powdered cocaine into plastic bags. When Williams said Joseph had promised two free bags, Tracy replied he already knew about the sale arrangements. Joseph then came into the apartment, counted out nineteen bags, and gave them to the Detective. Williams then gave Joseph $850.
Williams returned to the apartments on May 11,1990. Joseph told the Detective he was out of drugs, but urged Williams to come again after Joseph had spoken to his supplier. Joseph, however, was not there when Williams returned; Williams spoke with Tracy, who said he also was waiting for Joseph. Tracy said, “[W]e ain’t got shit” and asked Williams to return later. Government’s Exhibit 11. When Williams came back, Tracy told him that Joseph was still absent. In conversation with the Detective, Tracy agreed he and others had been turning away business and said, “we can lose about two or three thousand dollars.” Id. Williams left without making a purchase.
Four days later Tracy told Williams that they had $8,000 worth of cocaine left to sell and were down to their last eighteen bags of the drug. When Williams said hе needed to buy at least fifty bags of cocaine, Tracy told him to come back later that day. When Williams returned and knocked on an apartment door, Tracy came outside. Joseph joined them and the three began a conversation during which Joseph told Williams he had $500 worth of cocaine to sell. When Williams agreed to buy it, Joseph took a package from his pocket and handed it to Tracy. The three entered the apartment and went into a bedroom, where Tracy removed eleven smaller packages from the one Joseph had given him. Joseph told Williams his supplier would not sell an ounce of cocaine, and added that Joseph was trying to buy it from another source and turn it into cocaine base. Tracy then gave Williams ten packets of cocaine, for which the Detective gave Tracy $500.
Williams’s last cocaine purchase was made in the afternoon of May 30, 1990. Williams went to the complex and spoke to Tracy. During the conversation, one of Tracy’s relatives took him aside and claimed that Williams was a police officer. When confronted with this statement the Detective, although he had previously arrested the relative, denied it. Apparently, Williams was believed: he then purchased thirteen pieces of crack from both men for $200, which he gave to Tracy.
II
The first issue arises from an incongruity between the opening argument of the Assistant United States Attorney (AUSA) and part of Williams’s testimony. The AUSA told the jury, “[Tjhe police have a narcotics investigation ... in response to an informant’s information that a Tracey [sic] Watson is selling crack at that location.” Tr. at 5. Williams, at the outset of his testimony, testified about how his investigation began: “[A confidential] infor *986 mant advised me that heavy cocaine sales was [sic] occurring at that address with brothers being involved, one Tracey [sic] Watson and Joseph Watson.” Id. at 13. On cross-examination, Williams insisted he told the AUSA that the informant had named both brothers. Because the AUSA had not mentioned Joseph Watson in his opening statement, defendants moved to call the AUSA as a witness for the purpose of impeaching Williams. The brothers argue that the District Court’s denial of their motion erroneously deprived them of critical evidence that would have damaged Williams’s credibility.
Whether a defending or prosecuting attorney may testify in a case he is trying is within the discretion of the district court.
United States v. Buckhanon,
The AUSA’s testimony was not vital evidence. Defendants argue that because neither Williams’s tape recordings nor his police report mention Joseph, the Detective’s testimony “raised” a “suspicion” that his attribution of Joseph’s name to the informant’s tip was an impromptu alteration of the evidence. Brief of Tracy Watson at 13, Brief of Joseph Watson at 8. However, defendants’ offer of proof showed only that while Williams and the AUSA had many conversations about the brоthers, the AUSA could not recall if Williams said the informant also had mentioned Joseph. This testimony would not have contradicted Williams and would not have given the jury additional facts with which to evaluate the Detective’s credibility. In these circumstances, we do not believe the AUSA’s stated lapse of memory was vital evidence.
Compare Prantil,
In addition, we note the District Court’s ruling actually left the brothers in a position superior to the one they sought to obtain by the AUSA’s testimony. Without an explanation that the incongruity between Williams’s testimony and the opening argument may well have been produced by the AUSA’s forgetfulness, the brothers were in a more effective position to employ this difference to attack Williams, as Joseph’s counsel did during his closing argument.
2
Perhaps because Williams’s attri
*987
bution of Tracy’s name to the informant’s tip was undisputed, Tracy’s attorney did not dwell upon this matter. Tracy, however, had the same opportunity to suggest Williams manufactured evidence against his brother and was therefore capable of doing so against himself. The District Court did not commit a “ ‘clear and prejudicial abuse of discretion,’ ” and we find no error on this point.
Green Forest,
Ill
Defendants also claim the District Court erred in permitting Detective Williams to testify about the informant’s tip. They contend this testimony contained “a hearsay accusation” that violated their right to confront the witnesses against them. Brief of Joseph Watson at 10; Brief of Tracy Watson at 15.
3
It is elementary that “[a]n out-of-court statement is not hearsay, however, if it is offered for the limited purpose of explaining why a police investigation was undertaken.”
United States v. Brown,
IV
Tracy contends the evidence was insufficient to convict him. In evaluating this claim “we must assume that the government's evidence is truthful and valid, and we must give the government the benefit of all reasonable inferences which may logically be drawn from that evidence.”
United States v. Warbonnet,
Regarding the conspiracy conviction, 21 U.S.C. § 846 does not require the government to prove that Tracy acted in furtherance of а conspiracy. The evidence must only show that he “entered into an agreement with at least one other person and that the agreement had as its objective a violation of the law.”
United States v. Foote,
Viewed in the light most favorable to the jury’s decision, the evidence shows that Tracy and Joseph twice pooled their cocaine in order to meet Williams’s requirements. On one of these occasions Williams handed the entire purchase price to Joseph. After the other sale Williams gave the money to Tracy, who then divided it with Joseph. On two other occasions Tracy referred Williams to his brother for cocaine sales. During the discussion Tracy had with Williams on April 30 about selling drugs in Springfield, the defendant referred to a “partner.” Indeed, Tracy repeatedly used plural pronouns when discussing cocaine sales with the Detective. For example, on May 11 Tracy told Williams he was waiting for Joseph (who had left to obtain cocaine) and said “we can lose about two or three thousand dollars.” Government’s Exhibit 11. On two other occasions Trаcy personally executed drug sales that Williams had arranged with Joseph, and during one of these sales Tracy indicated Joseph had instructed him to give Williams free cocaine. This evidence is more than sufficient to sustain Tracy’s conspiracy conviction.
See, e.g., Foote,
As to the possession charges, Tracy concedes that Williams’s testimony provides evidence of guilt. But he claims no reasonable trier of fact could have relied on Williams’s statements. Although ordinarily witness credibility is left completely to the jury and is beyond appellate review,
United States v. Brown,
Tracy begins his argument by stating that “the bulk” of Williams’s testimony “concerned the nature and content of the taped conversations.” Brief of Tracy Watson at 8. He claims Williams admitted that he may not have listened to the tapes of *989 this extended drug investigation until he transcribed them months later, and argues this fact provides ample reason to doubt Williams’s testimony. Elsewhere in his brief Tracy notes that although Williams testified about Tracy’s participation in several drug deals, Williams did not testify that the defendant’s voice was recorded by the tapes of those deals. Tracy further points out the police did not attempt to determine whether his fingerprints were on the packages of drugs Williams received; that none of the other officers working with Williams was called to testify about the transactions; that no photographs were taken of Tracy at the apartment complex; and that although Williams supplied the brothers with money whose serial numbers had been recorded, none of these bills was recovered. Tracy concludes his convictions should be reversed because these alleged implausibilities, contradictions, and lack of corroborating evidence would give “the reasonable trier of fact a reason to doubt” his guilt. Brief of Tracy Watson at 9.
These arguments do not withstand scrutiny. Detective Williams was not a scribe testifying about the contents of records. He was a participant in the relevant events and spoke from his personal knowledge about each and every transaction. Tracy’s claim that Williams testified he may not have listened to the tapes for months after they were made is astonishing: on cross-examination, Williams told Tracy’s counsel that when he finished each purchase, he listened to the tapes of the transactiоn. Tr. at 120. Indeed, the tapes were merely corroborating evidence and although parts of them are indistinct (because of static, low voices, street noise and background music), they contain many audible, incriminating statements. The transcriptions, which were offered merely as interpretive aids, are accurate and duly note these indistinguishable sections. The mere fact that the machines employed by the police did not record Tracy’s voice during several transactions would not compel any rational jury to disbelieve Williams’s testimony that Tracy participated in them. Likewise, thе absence of corroborating physical evidence such as fingerprints or photographs does not make a witness’s testimony inherently unbelievable.
Cf. United States v. Sanders,
While it may have been possible for a rational jury to have disbelieved Detective Williams’s testimony and thus to have acquitted Tracy,
Jackson
does not demand that the government’s evidence be so conclusive and unimpeachable that no reasonable person could have rejected it; the case only prohibits reliance on evidence sо untrustworthy that no rational person could have believed it.
Jackson,
V
Finally, Tracy argues the District Court erroneously concluded that his criminal history placed him in Sentencing Guidelines Category IY. The relevant facts are undisputed. On August 26, 1987, Tracy was convicted of theft in the St. Louis County Circuit Court and was placed on probation; his probation was revoked in August 1989, at which time he received a three-year sentence. Approximately two months later, in October 1989, Tracy pleaded guilty to possession of cocaine in the St. Louis City Circuit Court and received a two-year sentence; this sentence was ordered to run concurrently with the sentence for Tracy’s theft conviction. Tracy agrees he deserves three criminal history points for his theft sentence, but challenges receiving three additional points for his cocaine sentence. He argues that since *990 the cocaine sentence was made concurrent with the theft sentence, both sentences were imposed in “related cases” under Guidelines section 4A1.2(a)(2), which requires sentences in such cases to be treated as only one sentence when computing a defendant’s criminal history score. U.S.S.G. § 4A1.2(a)(2) (Nov.1990).
Application Note 3 to section 4A1.2 instructs that “[c]ases are considered related if they (1) occurred on a single occasion, (2) were part of a single common scheme or plan, or (3) were consolidated for trial or sentencing.” U.S.S.G. § 4A1.2, comment, (n. 3) (Nov.1990);
see also
U.S.S.G. § 1B1.7 (Nov.1990) (indicating that commentary “may interpret the guideline or explain how it is to be applied”). Tracy’s theft and cocaine offenses were not committed on a single occasion, nor is there evidence suggesting they were part of a common scheme or plan. The only possible way to consider them “related cases” is to accept Tracy’s contention that they “were consolidated for trial or sentencing.” U.S.S.G. § 4A1.2, comment, (n. 3) (Nov.1990). The District Court’s decision regarding the legal interpretation of section 4Al.2(a)(2) is reviewed
de novo. United States v. West,
The circumstances described by the first and second elements of Application Note 3 to Guidelines section 4A1.2 depend upon the character of a defendant’s criminal conduct. Therefore, they are distinct from the third element, whose relevance depends upon whether the determination of guilt or the imposition of punishment for two or more of the defendant’s prior offenses were combined. Consequently, in employing this part of the Application Note we must look to the court records of the defendant’s prior offenses to see whether a decision was made to consolidate those offenses for trial or sentencing. The decision to consolidate trials is expressed by the defendant’s trial under one multiple-count indictment or information, or by a single trial on charges against the defendant contained in multiple indictments or informations. Similarly, the decision to consolidate sentencings is expressed by the dedication of a single proceeding to imposing punishment for verdicts reached in two or more trials.
See United States v. Manuel,
That Tracy was convicted in two separate proceedings and was sentenced in twо separate proceedings by different courts having separate jurisdictions is enough, standing alone, to support the District Court’s decision.
See Manuel,
944
*991
F.2d at 416 (holding sentencings were not consolidated because defendant’s “sentences were not imposed in the same proceeding” and because they were imposed by separate jurisdictions);
United States v. Rivers,
VI
The convictions of Tracy and Joseph Watson are affirmed. Only Tracy Watson appealed his sentence; that sentence is affirmed.
Notes
. The Honorable George F. Gunn, Jr., United States District Judge for the Eastern District of Missouri.
. Counsel argued that Williams “put in the police report yes, we went out there. The reason; an informer told him there was a Tracey [sic ] Watson out there selling drugs. That’s in the police report, in a taped monologue_ Sometimes what you say in these opening statements can embarrass you. I think this is an excellent example in [the AUSA’s] opening statement.... *987 Now, here much later we have a statement that, well, there was evidence that the Watson brothers, Tracey [sic] and Joseph were out there selling dope. Now, I think Mr. Williams was asked a simple question, based on the opening statement, based on the police reports, based on a taped monologue, Officer Williams before yesterday, did you ever tell [the AUSA] that you had one iota of information or that anybody had claimed that Joseph Watson was out there selling narcotics? Well, I had to ask the question twice, if you’ll recall, because there was some hemming and hawing around, a real vague answer the first time. And well, the second time around he says well, I told him. Well, we’ll see what [the AUSA] has to say about this in his сlosing argument.” Tr. at 204-06.
. Tracy Watson did not interpose a contemporaneous objection to this testimony, and was therefore open to an argument that he waived this claim of error.
United States
v.
Kragness,
. Although this rule is fairly rigid, we note that district courts may use the facts supporting an unsuccessful consolidation argument to impose a lesser sentence than that recommended by the Guidelines if the defendant’s criminal history has been over-represented.
See United States v. Senior,