I thought this smelled like totally useless Reddit-style cynical speculation, and 30 seconds of Googling confirmed my suspicion. No state allows admitting polygraph results without both parties' consent. Federal courts may or may not allow them depending on the judge, but if the judge allows them then the defendant is free to submit their passed polygraph (for whatever that's worth) just as equally as the prosecution is free to submit a failed one.

That's my understanding as well.

https://www.hg.org/legal-articles/is-a-polygraph-test-admiss...

> admissible or not, it'll be brought up

That's not how it works, and even a public defender working 20 hour days who doesn't know their defendant's name would be able to get a mistrial.

In the stairwell outside the court room:

"Look, I know your guy went for a polygraph, but you've not brought it up, so I assume he didn't do well. Here's what I can offer..."