Lewis Aaron Cook was convicted by a jury of two counts of possession of cocaine with intent to distribute in violation of 21 U.S.C. § 841(a)(1) (1988), and of maintaining a place for the purpose of distributing controlled substances in violation of 21 U.S.C. § 856(a) (1988). He was sentenced to twenty years and ten months. Mr. Cook appeals both his conviction and sentence, citing numerous errors below. We affirm.
In July 1989, the Tulsa Police Department investigated Mr. Cook’s involvement with drugs. On July 25, Officer Mark McCrory of the Tulsa Police initiated a controlled drug buy from Mr. Cook by a confidential informant. Immediately thereafter, Officer McCrory obtained a search warrant for Mr. Cook’s apartment. The police searched his apartment that evening and arrested and charged him with state narcotics violations. He was released on bond pending a preliminary hearing in state court scheduled for August 24. On August 21, the police again searched Mr. Cook’s residence, arrested him along with Yvonne Cross, and charged him with additional state narcotics offenses. Pursuant to conversations between Officer McCrory, Officer Mark Siebert of the Federal Bureau of Alcohol, Tobacco and Firearms, and the United States Attorney’s Office, a federal investigation was initiated. Based on the drug trafficking underlying the state charges, Mr. Cook was indicted on September 6, and charged with federal narcotics violations. On September 8, Mr. Cook, out on bond again, was arrested in his car along with Ruth Ann Zachary and Patricia Swimp by federal and state law enforcement personnel. His state charges were dismissed later that month over his objection.
I.
Mr. Cook first argues that the dismissal of his state charges and the subsequent prosecution of this case in federal court violate the Due Process and Equal Protection Clauses of the United States Constitution. He contends that he was denied due process when his prosecution under an applicable federal statute subjected him to a harsher penalty than prosecution under the applicable state statute would have. He also contends that the federal prosecution denied him equal protection because the government prosecuted Ms. Zachary for the same conduct in state court, even though she was arrested along with Mr. Cook on September 8.
We recently held that a defendant’s due process rights are not violated by the federal government’s decision to prosecute under a federal, rather than state, statute, notwithstanding the harsher penalties.
United States v. Andersen,
We likewise find no merit in Mr. Cook’s argument that his Fourteenth Amendment right to equal protection was violated by the decision to prosecute him, and not Ms. Zachary, under a federal stat
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ute. Absent a showing of discriminatory purpose and effect, Mr. Cook does not state an equal protection claim.
Wayte v. United States,
II.
Mr. Cook next challenges the sufficiency of the affidavit in support of the search warrant issued on July 25, alleging that it contained insufficient facts to sustain a probable cause determination. Specifically, he argues that the failure of the affiant, Officer MeCrory, to test the substance bought by the confidential informant is fatal to the affidavit’s sufficiency.
When reviewing the validity of a search warrant, we must determine whether, under the totality of the circumstances presented in the affidavit, the magistrate had a substantial basis for. finding a fair probability that contraband or other evidence of a crime would be found in the place to be searched.
Illinois v. Gates,
Based on the totality of the circumstances, we conclude that substantial grounds existed for believing that cocaine could be found in Mr. Cook’s apartment. Although Officer MeCrory did not conduct a field test on the substance that the confidential informant brought to him from Mr. Cook’s apartment, he had been trained to recognize cocaine and had been personally involved in numerous cocaine arrests. Moreover, Officer MeCrory was able to control and observe the circumstances under which the confidential informant obtained the substance, and he had the benefit of the informant’s opinion that the substance was cocaine. A magistrate is enti-
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tied to rely on the expert opinions of officers when supporting factual information is supplied in the affidavit.
See United States v. Medlin,
III.
Mr. Cook next contends that the testimony of co-defendant Yvonne Cross, who had pled guilty, was inherently contradictory, and that the trial court therefore erred in admitting it. Mr. Cook had supplied cocaine to Ms. Cross with whom he had been living for about a month prior to their arrest. She served as a lookout while Mr. Cook dealt cocaine out of his apartment. Mr. Cook once had her test cocaine he purchased for resale. As part of her plea bargain, Ms. Cross agreed to cooperate with the government and to testify against Mr. Cook. When called to the stand, however, she initially refused to testify against him and then did so only grudgingly and under threat of contempt. On cross-examination, she maintained that her prior testimony had been a lie and that she felt pressured by the government. On redirect, Ms. Cross again recanted her initial testimony. The district court denied Mr. Cook’s motion to strike Ms. Cross’ testimony.
We may reverse an evidentiary ruling only if we find that the district court abused its discretion.
United States v. Temple,
Although Ms. Cross’ testimony was contradictory at times, it purported to relate to circumstances within her personal knowledge. And while the testimony of a drug abuser may be suspect for a number of reasons, drug abuse alone does not render a witness incompetent.
See United States v. Smith,
IV.
We find no merit in Mr. Cook's argument that the district court committed reversible error when it refused his request for special instructions with regard to the testimony of Ms. Cross and Ms. Swimp. We review the jury instructions in light of the record as a whole to determine whether they provided the jury with the requisite understanding of the issues presented at trial and the legal standards applicable to those issues.
Big Horn Coal Co. v. Commonwealth Edison Co.,
Mr. Cook next argues that the district court’s refusal to instruct the jury about the particular infirmities of a drug addict’s testimony denied him a fair trial. The transcript of the charging conference reveals that the government objected to the portion of Mr. Cook’s proposed instructions that read:
“An addict has a constant need for supply of drugs and for money to support his and her habit and also may have abnormal fear of imprisonment in which his or her supply of drugs might be cut off. These are special circumstances which you may consider in weighing testimony of this kind.”
Rec., vol. VI, at 544.
While “[a]s a general rule, prudence dictates the giving of an addict instruction whenever the prosecution has relied upon the testimony of a narcotics addict,” whether refusal to so instruct is reversible error depends on the particular facts of each case.
Smith,
“In deciding what the facts are, you must consider all the evidence. In doing this, you must decide which testimony to believe and which testimony not to believe. You may disbelieve all or any part of any witness’ testimony. In making that decision, you may take into account a number of factors including the following:
1. Was the witness able to see, or hear, or know the things about which that witness' testified?
2. How well was the witness able to recall and describe those things?
3. What was the witness’ manner while testifying?
4. Did the witness have an interest in the outcome of this case or any bias or prejudice concerning any party or any matter involved in the case? The testimony of a witness who provides evidence against a defendant for personal advantage must be considered with great care. You must decide whether the credibility of the witness’ testimony was affected by his personal interest.
*295 5. How reasonable was the witness’ testimony in light of all the evidence in the case?
6. Was the witness’ testimony contradicted by what that witness had said or done at another time, or by the testimony of other witnesses, or by other evidence? In deciding whether or not to believe a witness, keep in mind that people sometimes forget things. You need to consider therefore whether a contradiction is an innocent lapse of memory or an intentional falsehood, and that may depend on whether the contradiction concerns an important fact or only a small detail.
7. Was the witness’s testimony bolstered by the fact he or she had said essentially the same thing on more than one occasion? If so, it may be reason for you to believe the testimony of that witness.
“These are some of the factors you may consider in deciding whether to believe testimony.
“The weight of the evidence presented by each side does not necessarily depend on the number of witnesses testifying on one side or the other. You must consider all the evidence in the case, and you may decide that the testimony of a smaller number of witnesses on one side has greater weight than that of a larger number on the other.
“All of these are matters for you to consider in finding the facts.”
Kec., vol. I, doc. 37 at 8-9. The jury received an additional instruction relating to the testimony of Ms. Swimp:
“The testimony of an admitted perjurer should always be considered with caution and weighed with great care.”
Id. at 10.
Under the circumstances of this case, we conclude that the failure to give the addict instruction proffered by Mr. Cook was not reversible error. The drug abuse of both Ms. Cross and Ms. Swimp was revealed to the jury, and the district court gave a general credibility instruction alerting the jury to the potential for untrue testimony to gain personal advantage.
See Smith,
Y.
Mr. Cook next contends that the district court erred in adopting the probation officer’s estimate of the quantity of drugs involved in his offense. Although he admits it is proper under the Sentencing Guidelines for the court to estimate the amount of cocaine attributable to his activities,
see United States v. Easterling,
The government must prove the drug quantity by a preponderance of the evidence.
See Easterling,
The probation officer testified at the sentencing hearing that he relied on information provided by Ms. Cross on three different occasions to determine that Mr. Cook sold between $1000-$2000 worth of cocaine daily.
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Ms. Cross’ testimony in this regard was consistent throughout the proceedings. Moreover, she previously had relayed the same information in an interview with the Assistant United States Attorney, and had attested to the veracity of her presentence report, containing the same figures. Ms. Cross was quite familiar with Mr. Cook’s drug trafficking. We conclude that the district court’s factual determination is supported by the record and that the information upon which the court relied contains sufficient indicia of reliability.
See United States v. Frondle,
VI.
Finally, Mr. Cook argues that the district court erred in relying on the testimony of Ms. Swimp to enhance his base offense level for obstruction of justice. We review a court’s decision to enhance a sentence for obstruction of justice for clear error when the issue raised concerns a determination of fact.
See United States v. McCann,
The judgment of the district court is AFFIRMED.
Notes
. It is apparent from Mr. Cook’s argument to the district court and on appeal that he was primarily concerned with the witnesses’ ability to comprehend events while they were impaired. However, the language of his proffered instruction, and of the instructions discussed in the cases he cites,
see Government of Virgin Islands v. Hendricks,
. The probation officer used the minimum estimation of $1000 and multiplied it by 25, the number of days Ms. Cross had lived with Mr. Cook and had aided him in his cocaine trafficking. By estimating that each crack cocaine transaction cost $30, the probation officer arrived at a base level of 34. The officer also testified that he used as a measuring stick the amount of cash seized from Mr. Cook during his three arrests, which was approximately $2,000. These are appropriate methods by which to estimate the magnitude of Mr. Cook's cocaine business. See United States Sentencing Comm'n Guidelines Manual § 2D 1.4, Application Note 2 (1990).
