Willie Barnes appeals his conviction on two counts of unlawful delivery of a controlled substance, RCW 69.50.401(a)(l)(i). He claims he was unconstitutionally denied the right to confront a witness and the trial court improperly instructed the jury on the effects of his decision not to testify. We affirm.
On September 8, 1986, police officers conducted a controlled buy of cocaine in Pasco. A similar operation on September 22 yielded heroin. The buyer on both occasions was Dale Redmond, a police informant who at trial identified Mr. Barnes as the seller. Police officers confirmed some details of the operations, but Mr. Redmond, as purchaser, was the only witness who linked Mr. Barnes directly to the sales.
Before trial, Mr. Barnes' attorney stated his intent to impeach Mr. Redmond with two undated and unsigned letters reputedly written by Mr. Redmond in 1971. The letters attempted to induce a witness against Mr. Redmond in an unrelated case to give false testimony, or withhold true testimony, and threatened death to the witness and his family. The prosecutor objected: he had no prior knowledge of any letters, their date was too remote, their relevancy was questionable, and the material was prejudicial. The trial court treated the statement of intent as a motion and denied it without stating a reason.
*538During redirect examination, the prosecutor asked Mr. Redmond if he knew the meaning of a witness' oath, and Mr. Redmond responded affirmatively. Prompted by the question and answer, Mr. Barnes' attorney again asked the court to allow him "to use the letter that he [Mr. Redmond] wrote in 1971 to impeach him about his belief in that oath." The prosecutor again objected on the ground of relevancy to the question of Mr. Redmond's understanding of the meaning of the oath. The court again denied the request, observing only that "on the basis of the time that's elapsed on the date of those letters . . . the prejudicial effect of those would outweigh the probative value."
On recross examination the defense established that Mr. Redmond was using drugs in September 1986 while participating in the controlled buys.1 Mr. Barnes declined to testify, and presented no other evidence in his own behalf. Mr. Barnes' attorney focused exclusively on Mr. Redmond's credibility in closing argument. The jury returned a guilty verdict after 1V2 days of deliberation.
Mr. Barnes now contends he was denied his right to confront the key witness against him. The sixth amendment to the United States Constitution and Const, art. 1, § 22 (amend. 10) grant criminal defendants the right to confront and cross-examine adverse witnesses, subject to the State's interest in seeing that the evidence is not so prejudicial as to disrupt the fairness of the factfinding process. State v. Hudlow, 99 Wn.2d 1, 15, 659 P.2d 514 (1983). A "compelling state interest" test has been adopted if a court ruling is challenged on grounds it unduly restricted the defendant's right to confrontation. If the evidence is characterized as being of "high probative value", there can be no state interest compelling enough to preclude its introduction. Hudlow, at 16 (citing Davis v. Alaska, 415 U.S. *539308, 39 L. Ed. 2d 347, 94 S. Ct. 1105 (1974); Chambers v. Mississippi, 410 U.S. 284, 35 L. Ed. 2d 297, 93 S. Ct. 1038 (1973)).
A compelling state interest here includes an assurance that witnesses who come forward with evidence of a crime will not be discouraged from testifying because a prior conviction or misconduct may be revealed. State v. Martinez, 38 Wn. App. 421, 424, 685 P.2d 650, review denied, 102 Wn.2d 1020 (1984). In Martinez the defendant attempted to impeach the victim with a mid-1960's felony conviction for passing bad checks. The court ruled the defendant's interest in the impeachment through use of the prior conviction was minimal because of other impeachment evidence already admitted. We find that argument to be persuasive here, as there was other evidence of a sufficient quantity before the jury to impeach Mr. Redmond.
The admission of the letters was a matter of discretion by the trial court and will not be disturbed here absent abuse. State v. York, 28 Wn. App. 33, 36, 621 P.2d 784 (1980). In York, the trial court allowed the State to elicit the employment history of the only witness against the defendant. The defense sought to elicit, on cross examination, that the witness had been fired from a job because of irregularities in his paperwork and his general unsuitability for the job. This court reversed the trial court's order in limine, stating the defendant had been precluded from any cross examination of the witness' credibility, which was critical to the defendant's case. York, at 37. That case is distinguished from the facts here because the trial court allowed extensive cross examination of Mr. Redmond's past, including reference to his prior convictions and personal drug use during the controlled buy.
The trial court rejected the letters on the basis of the time elapsed and the fact their prejudicial effect outweighed their probative value. The letters were admittedly written in 1971 and did not involve the parties or the facts before the court. Defense counsel did not have them marked for identification nor does the record reveal how he *540intended to use them. If he intended to use them as extrinsic evidence attacking Mr. Redmond's credibility, such use would be improper under ER 608(b).2 If defense counsel intended to use them as the subject matter of cross examination under ER 607 to impeach Mr. Redmond, one of two results were possible: (1) If Mr. Redmond affirmed that he had sent letters attempting to suborn perjury of a witness, use of the letters themselves would then have been unnecessary. (2) If Mr. Redmond had denied the attempt to suborn perjury, the inquiry would have been at an end because " [t]he cross-examiner must 'take the answer' of the witness and may not call a second witness to contradict the first witness." (Footnote omitted.) 5A K. Tegland, Wash. Prac., Evidence § 232(6), at 212 (3d ed. 1989), and cases cited. Authentication could only have been accomplished by calling a second witness. Additionally, no request was made to question Mr. Redmond concerning the subornation attempt, using the letters as the foundational justification for asking the question. See K. Tegland § 232(1), at 205.
Mr. Barnes also urges us to consider whether the letters themselves were properly excludable under ER 403:
Although relevant, evidence may be excluded if its probative value is substantially outweighed by the danger of unfair prejudice, confusion of the issues, or misleading the jury, or by considerations of undue delay, waste of time, or needless presentation of cumulative evidence.
He asserts the letters are relevant under ER 402 and not excludable within the exercise of the court's discretion by application of one or more of the six safeguards identified in ER 403. He does this apparently because the trial court's stated reason for rejecting the use of the letters was that their probative value was substantially outweighed by the danger of unfair prejudice. There is no doubt that the unfair prejudice in this case must be focused on Mr. *541Barnes. State v. Allen, 50 Wn. App. 412, 422 n.3, 749 P.2d 702, review denied, 110 Wn.2d 1024 (1988). It most surely is not applicable to the witness, nor to the State, nor to the truthfinding function itself. Hudlow, at 13. Thus, the stated reason for the court's rejection of the evidence is erroneous. But, this court may affirm on any correct legal basis. Sprague v. Sumitomo Forestry Co., 104 Wn.2d 751, 758, 709 P.2d 1200 (1985); State v. Armstead, 40 Wn. App. 448, 449-50, 698 P.2d 1102 (1985).3 That correct basis includes the compelling state interest previously noted and proper exclusion under ER 608(b).
We note the defense was fully able to develop the issue of Mr. Redmond's credibility through the multiple questions concerning his use of drugs, payment for his services by the police, use of the payment to purchase drugs for himself, prior conviction of forgery and deferred prosecution for shoplifting charges. The length of time the jury deliberated before reaching its verdict of guilty suggests, when accompanied by the closing argument of defense counsel, a thorough examination of the issue of credibility before the verdict was reached. The use of other relevant evidence has been held to be a factor in limiting cross examination. State v. Allen, supra at 422; Martinez, at 424. Thus, we find no error.
In Mr. Barnes' second assignment of error, he contends the court incorrectly instructed the jury on the effect of his *542decision not to testify. When requested, a court must instruct the jury not to draw an adverse inference from the defendant's failure to testify. Carter v. Kentucky, 450 U.S. 288, 300, 67 L. Ed. 2d 241, 101 S. Ct. 1112 (1981). Mr. Barnes requested the following instruction:
The Defendant is not compelled to testify, and the fact that the Defendant has not testified cannot be used to infer guilt nor to prejudice him in anyway [sic].
The court instead instructed the jury in accord with 11 Wash. Prac., WPIC 6.31 (Supp. 1986):
The Defendant is not compelled to testify, and the fact that the Defendant has not testified cannot be used to infer guilt and should not prejudice him in anyway [sic].
The court's instruction is essentially the same as the one requested in Carter, 450 U.S. at 294. The issue in Carter was not the wording of the instruction itself, but whether the defendant was entitled to a "no inference" instruction on request.
Mr. Barnes' objection to the court's instruction is that the words "should not" are essentially permissive; the jury thus could have interpreted Mr. Barnes' refusal to testify as supportive of Mr. Redmond's credibility. He relies on United States v. Eiland, 741 F.2d 738 (5th Cir. 1984), which held the trial court's refusal to give a "no inference" instruction was not harmless error. Here, by contrast, the court gave a "no inference" instruction. The issue is whether the words "should not" misled the jury, as Mr. Barnes contends. We are not convinced the jury could have been misled by the instruction in any way as to Mr. Redmond's testimony. The instruction properly reflects the admonition "that a defendant must pay no court-imposed price for the exercise of his constitutional privilege not to testify." Carter, 450 U.S. at 301; see Griffin v. California, 380 U.S. 609, 14 L. Ed. 2d 106, 85 S. Ct. 1229, reh'g denied, 381 U.S. 957, 14 L. Ed. 2d 730, 85 S. Ct. 1797 (1965). Indeed, the auxiliary verb "should" expresses an obligation or necessity that a defendant not be prejudiced by deciding *543not to testify. State v. La Porte, 58 Wn.2d 816, 823, 365 P.2d 24 (1961).
The judgment is affirmed.
Munson, J., concurs.
On cross examination it had also been established that Mr. Redmond was paid by police to participate in the controlled buys; that he was using these payments to buy drugs for his own use; that he was given deferred prosecution on a shoplifting charge; and that he had a prior conviction for forgery.
ER 608(b) provides, in part:
"Specific instances of the conduct of a witness, for the purpose of attacking or supporting his credibility, other than conviction of crime as provided in rule 609, may not be proved by extrinsic evidence."
It is noted that Mr. Redmond pleaded guilty to a charge of bribery, not intimidating or tampering with a witness, on the basis of the 1971 letters. However, the conviction would not have been admissible because it was more than 10 years old. ER 609(b) provides:
Evidence of a conviction under this rule is not admissible if a period of more than 10 years has elapsed since the date of the conviction or of the release of the witness from the confinement imposed for that conviction, whichever is the later date, unless the court determines, in the interests of justice, that the probative value of the conviction supported by specific facts and circumstances substantially outweighs its prejudicial effect. However, evidence of a conviction more than 10 years old as calculated herein, is not admissible unless the proponent gives to the adverse party sufficient advance written notice of intent to use such evidence to provide the adverse party with a fair opportunity to contest the use of such evidence.