Don't think of a pink elephant
You're out of your seat the minute the witness mentions that your client was in prison, or the cop testifies that he believes the victims were telling the truth. Your objection is met with the judge sustaining it, then turning to the jury and intoning, "You are instructed to disregard that testimony." After your client is convicted, you follow up with the appellate lawyer a year later and, sure enough, he tells you that the appeals court rejected the claimed error regarding the inadmissible testimony. Oh, sure, the panel huffed and puffed about how it was indeed error, but then comes the line all of us know so well. No prejudice, because "the jury is presumed to follow the judge's instructions."
We all know better than that, even the judges who write those words. Here's Supreme Court Justice Jackson's assessment of their value: "The naïve assumption that prejudicial effects can be overcome by instructions to the jury . . . all practicing lawyers know to be unmitigated fiction."
Telling a jury to disregard evidence is like telling them to not think of a pink elephant. The human mind isn't built that way. In fact, those same appellate courts will reject an argument that counsel was ineffective for not requesting a curative instruction. Why? Because not requesting a curative instruction might be a tactical gambit, in the belief that such an instruction will only remind the jury of what they're supposed to forget. We all know that such instructions are a waste of time.
Maybe not, it turns out, at least according to a law review article by a law professor at Berkeley, one of the things I ran across during my wanderings in the desert these last six weeks. (It's a preliminary draft, and the author says not to cite, quote, or circulate without permission. I checked and one of my jobs isn't to sit down and write a letter asking for permission to do something - nor is it in my character - so we'll just talk about it instead.)
One of the things we learn is that the empirical evidence on the effect of curative instructions are decidedly mixed. There are some serious methodological and bias flaws in a number of studies that have been done, but even discounting that several show that juries do take such instructions seriously. After all, there's a difference between telling someone to forget something and telling him to disregard it. At the least, there's a decent chance that if a juror brings up the tainted evidence in deliberations, somebody else will say, "But the judge said we're not supposed to consider that."
On the other hand, that's for curative instructions, which tell the jury to disregard the evidence. There are also limiting instructions, which tell the jury to use the evidence only in a certain way. For example, if a defendant with prior convictions testifies, the jury will be told to consider those convictions only in assessing his credibility, not for gauging his propensity to commit a crime. If prior acts testimony is introduced, the judge will instruct the jury to consider this only in proving absence of mistake, identity, motive, or one of the other exceptions to propensity under EvidR 404(B).
Bad news on this: the empirical evidence indicates that these types of instructions are almost always ineffectual, and sometimes counterproductive. That's because they're largely incoherent. The 404(B) instruction, for example, essentially tells the jury not to consider the evidence in deciding whether the defendant is the type of person who would commit the crime, but to consider it in deciding whether he committed the crime. The prior conviction instruction is little better; basically, the jury is told that they can use the prior convictions to determine whether the defendant is telling the truth when he denied he committed the crime, but not to determine whether he committed the crime.
So what to do? One thing to keep in mind is that the studies reveal that jurors were much more likely to discount evidence if given a reason for doing so. A judge saying, "The statement you've just heard is not reliable evidence, and for that reason, you will disregard it" is far more effective than just telling the jury to disregard it. So file some goofy motion before trial, like, "Motion to Explain Basis for Sustained Objections to the Jury," and make that argument. (If you intend on doing this, email me and I'll send you the links for those studies.) If you've got a decent judge, he'll at least think about it.
As for the limiting instructions, there's not much you can do, but that's because there's not much that can be done. Every defense lawyer representing someone with prior convictions will put his client on the stand only as a last resort, and if the jury finds out that your client committed a crime similar to the one he's on trial for, it's Game Over anyway.