In my experience it depends on the judge. Some judges have granted it; others may just instruct the jury to disregard. Don’t know what the judge in my case above would have done. Under the law PBT results were admissible at trial only under very narrow circumstances, and I was used to filtering them out of my testimony. But I’d heard of occasions when a rookie officer made the mistake of mentioning them and a mistrial resulted.
I’m not understanding this situation. If the witness did in fact rely on the test, how can a judge rule that the witness cannot mention that fact? Isn’t that telling the witness to disregard the oath to tell the whole truth? 
Because the test is not considered reliable enough to meet the standards for scientific evidence. Imagine if the cop wanted to say “I knew her was intoxicated because a fortune teller predicted it.” The Judge would let the jury hear that. Evidence is excluded all the time for all sorts of reasons. It might help establish probable cause for the arrest (in a pretrial hearing) but cannot be considered by the jury on the question of intoxication.
BTW, in many courts they don’t give the Hollywood oath. You just have to swear or affirm your testimony will be truthful. No “whole truth and nothing but the truth” or “god”.
Yes, but what if the officer did in fact rely on the roadside test, erroneously? If the judge has barred all reference to it, isn’t that foreclosing an important issue for the defence to explore?
How so? It’s proper (at least in Washington State) for an officer to use a PBT to establish probable cause and haul you in for a real BAC test. That’s the test the jury hears about. (The validity of the arrest isn’t a jury question).
The defense wants to limit the evidence of guilt. “My client stumbled once on heal to toe walk and you could smell alcohol in his breath. That’s it? That’s not much, is it?” “He also blew .15 on PBT” doesn’t help. I have seen lawyers try to get in a PBT that was below .08, but even then the judge says not reliable, inadmissible. Like the polygraph, it’s not getting to the jury (with rare exceptions).
How would that work? Rely on the prosecutor to decide what is exculpatory enough to merit disclosure? That’s a tricky issue- which I imagine would lead to appeals, assuming the defense eventually found out about the questionable evidence.
I don’t know. That’s my understanding of the difference between the Canadian and American rules, but I’m open to correction. The Canadian rule seems much easier to comply with, as it only involves a judgment call about the broad principle of “relevance o to the case”.
One defence counsel commented to me once that he’d had cases where the Crown had assumed that some fo the material they disclosed was inculpatory, but from the defence perspective, it actually helped support the defence’s case, which of course was not known to the Crown at the disclosure stage.
There was a doozy of a provoked mistrial in one of the Lincoln lawyer books, involving a faked assault by the defendant on his defense attorney, resulting in a mistrial and presumably intimidating a prosecution witness from testifying again against the defendant.
Probably you could get away with that only once…