Following a jury trial in Superior Court (Fauver, J.), the defendant, Sean Croft, was convicted of first degree assault, see RSA 631:1 (1996), and aggravated felonious sexual assault, see RSA 632-A:2 (1996). The defendant’s convictions also constituted a violation of a previous term of probation. In this consolidated appeal from both the convictions and the probation violation, the defendant argues that the superior court at his criminal trial erred: (1) in *77ruling, based on offers of proof, that an assistant county attorney could testify concerning a prosecution witness’s character for truthfulness; and (2) in admitting a letter, written by the defendant, whose probative value was substantially outweighed by its prejudicial effect. We affirm.
The jury could have found the following facts. On September 8, 1992, the defendant encountered the victim at a restaurant in Rochester and offered her pills for a headache. Previously, the defendant had stated to his girlfriend that he wanted to kill the victim as a result of her actions toward one of the defendant’s friends. At the restaurant, the victim ingested the pills, which the defendant failed to disclose were prescription sedatives. After the victim became unconscious, the defendant took her to his apartment where he brutally beat and kicked her, stabbed her in the leg, forced additional pills down her throat, and raped her.
I
The defendant’s first argument on appeal concerns a “ruling” by the trial court concerning the admissibility of proposed testimony from an assistant county attorney. At trial, Shane Grant testified that the defendant told him that the defendant had beaten and raped the victim. According to Grant, who had been incarcerated in the county jail with the defendant following the defendant’s arrest, the defendant made these statements in the presence of another inmate, Brian Ellis. At the conclusion of the State’s case, the defendant’s attorney informed the trial court of the defense’s intention to rest, rather than call Ellis. According to the defendant’s trial attorney, the decision to rest resulted from a previous “indication” by the trial court, during an unrecorded conference, regarding the admissibility of the prosecution’s evidentiary response to Ellis’ testimony.
On the record, the defendant’s attorney asserted that Ellis would have testified that the statements described by Grant were never made by the defendant in Ellis’ presence; that the prosecuting attorney would have countered Ellis’ testimony by calling a colleague, assistant county attorney Harry Starbranch, to testify as to his opinion of Grant’s truthful character; and that the prosecution’s use of an assistant county attorney to testify in such a manner would have been inappropriate. The trial court responded:
Let me just say we are not even at that point yet. I haven’t heard any of this testimony, and I haven’t even — obviously, once I hear it, Brian Ellis testifies, and Attorney Starbranch then decides to testify in rebuttal or the County *78Attorney calls him, in rebuttal, we’ll deal with those issues at the time. I can’t operate in a vacuum on this ....
The trial court further cautioned the defendant’s attorney against suggesting that,the court was somehow responsible for the defense’s decision not to call Ellis.
At that point, the prosecuting attorney interjected, explaining the State’s understanding that Ellis would impeach the credibility of Grant and essentially confirming the state of affairs described by the defendant’s attorney. According to the prosecuting attorney, the assistant county attorney would testify, based on his “several contacts and some dealings” with Grant, as to Grant’s character for truthfulness. The trial court again stated that it would not rule on the issue until it actually heard Ellis’ testimony and determined its significance with respect to the proposed rehabilitation testimony of the assistant county attorney. See N.H. R. Ev. 608(a).
Not satisfied with the trial court’s position, the defendant’s attorney pressed the court for a ruling on the appropriateness of the rehabilitation testimony under Rule 608(a) and, more particularly, on the propriety of such testimony from an assistant county attorney who had previously prosecuted the defendant. After further discussion, the trial court stated that the proposed testimony from the assistant county attorney would be permissible “if the proper foundation is laid consistent with Rule 608.” In addition, the trial court apparently concluded that testimony from Ellis directly contradicting Grant’s testimony would constitute the type of attack on Grant’s truthfulness that would authorize rehabilitation evidence concerning Grant’s truthful character. The defendant’s attorney then reiterated that Ellis would not be called as a defense witness.
On appeal, the defendant alleges three errors in the trial court’s “ruling” concerning the admissibility of the proposed testimony from the assistant county attorney. First, the defendant argues that the foundation for the rehabilitation testimony was insufficient under State v. Vachon, 139 N.H. 540, 543, 659 A.2d 426, 429 (1995), because the assistant county attorney merely had “dealings” and “contacts” with Grant. Second, the defendant contends that Ellis’ testimony would have directly contradicted Grant’s testimony and, therefore, would not have constituted the type of indirect attack on Grant’s general truthfulness that would have permitted evidence of Grant’s truthful character. Cf. State v. Ross, 141 N.H. 397, 400-02, 685 A.2d 1234, 1236-37 (1996). Third, the defendant argues that the trial court improperly condoned the prosecution’s “ploy of having a *79fellow prosecutor testify about the credibility of the State’s own witness.”
The State counters that none of these issues is preserved for our review because the trial court never ruled in the context of actual testimony. We agree. Although the record suggests that the trial court ultimately provided a conditional opinion on the admissibility of the assistant county attorney’s testimony, we endorse its initial refusal to “operate in a vacuum.” Because neither Ellis nor the assistant county attorney testified, “we find the claim of prejudicial error too speculative for adjudication.” State v. Bruneau, 131 N.H. 104, 115, 552 A.2d 585, 592 (1988); see also Luce v. United States, 469 U.S. 38, 41-42 (1984). Indeed, we have no way of knowing whether the defendant would actually have called Ellis to testify absent the trial court’s “ruling,” how Ellis would have testified, whether Ellis’ testimony and the cross-examination of Ellis would have triggered rehabilitation evidence under Rule 608(a)(2), whether the prosecution would have attempted to respond with testimony from the assistant county attorney, whether the prosecution would have established the foundational predicate for such testimony under Vachon, how the trial court ultimately would have ruled if the defendant interposed a specific and timely objection, and how the assistant county attorney would have testified. See United States v. Griffin, 818 F.2d 97, 104 & n.5 (1st Cir.), cert. denied, 484 U.S. 844 (1987); see also Bruneau, 131 N.H. at 115, 552 A.2d at 592.
Aware of the general rule against appellate review of hypothetical evidentiary errors, the defendant would have us distinguish this case on the grounds that the parties’ undisputed offers of proof were sufficiently specific to inform this court of the critical facts relating to the evidentiary issue and that the trial court’s “ruling” was erroneous as a matter of laiv. Neither ground advanced by the defendant provides a persuasive reason for departing from the general rule. The specificity of the offers of proof is irrelevant because “trial testimony [can], for any number of reasons, differ from the proffer[s].” Luce, 469 U.S. at 41 n.5; see also Griffin, 818 F.2d at 104. Characterizing the trial court’s “ruling” as an error of law in no way alters the principle that the admissibility of responsive evidence can only be determined after reviewing the actual testimony to which it would respond. See United States v. Nivica, 887 F.2d 1110, 1117 (1st Cir. 1989), cert. denied, 494 U.S. 1005 (1990).
*80II
The defendant next argues, based on New Hampshire Rule of Evidence 403, that the trial court erred in admitting a letter because its probative value was substantially outweighed by its prejudicial effect. The letter was written by the defendant to an inmate at the county jail after the defendant’s arrest and subsequent transfer from the county jail to the State Prison. In the letter, the defendant refers to his misconduct at the county jail, offers profanity-laced promises of revenge against employees at the county jail, describes himself as a member of “the new generation of prisoners,” identifies the State Prison as his “home for 6 to 15 years,” and portrays life at.the prison as relatively tolerable.
The State argues that the defendant’s objections at trial failed to preserve the Rule 403 argument that he currently advances. We agree. It is well settled that “a contemporaneous and specific objection is required to preserve an issue for appellate review.” State v. Russo, 140 N.H. 751, 753, 674 A.2d 156, 158 (1996) (quotation omitted). At trial, the defendant specifically objected to the letter on relevance grounds, mentioned “bad acts” and “character” concerns, and referred to New Hampshire Rule of Evidence 404(b). An objection on “bad acts” or Rule 404(b) grounds, however, has three potential bases. See State v. Bassett, 139 N.H. 493, 496, 659 A.2d 891, 894 (1995) (discussing three-pronged analysis for admissibility under Rule 404(b)). Relevance, the ground specifically raised by the defendant at trial, is only one of these bases; the Rule 403 balancing of probative value and prejudicial effect, a ground never identified by the defendant, is a separate basis. See State v. McGlew, 139 N.H. 505, 507, 658 A.2d 1191, 1193 (1995).
We conclude that the defendant’s specific objection on relevance grounds precludes his current attempt to broaden the scope of his challenge to the letter’s admissibility. Cf. State v. Mills, 136 N.H. 46, 49, 611 A.2d 1104, 1105 (1992) (specific objection concerning competency of child witness rendered other related arguments unpreserved). The fact that the trial court actually addressed the letter’s probative value and prejudicial effect is not alone dispositive, given the defendant’s initial failure to raise an objection based ■on prejudice, see State v. Winn, 141 N.H. 812, 813, 694 A.2d 537, 538 (1997), and his subsequent failure to object to the trial court’s balancing determination, cf. Mills, 136 N.H. at 49, 611 A.2d at 1105.
Finally, we assume without deciding that the defendant’s briefing of his Rule 403 argument adequately preserves a challenge to the letter’s relevance (the probative nature of the evidence forming part *81of the Rule 403 equation). Our inquiry ends, however, with the defendant’s recognition that the letter’s reference to State Prison as “home for 6 to 15 years” was marginally relevant to the assault charge.
Affirmed.
HORTON, j., and Broderick, j., concurred specially; the others concurred.