Fruit of the poison tree?
I think so, Under federal law, a prosecutor is required “to disclose exculpatory and impeachment information to criminal defendants and to seek a just result in every case.” Specifically, pursuant to Giglio v. United States, prosecutors are obligated to provide defendants with impeachment evidence, which includes, according to the DOJ’s guidelines, evidence of a witness’s biases, “[a]nimosity toward defendant,” or “[a]nimosity toward a group of which the defendant is a member or with which the defendant is affiliated.”