This is what I do in my own research, in which 70% of participants have told me all about how they committed crimes (assault, assault with a weapon, and theft) that never happened. Here’s how it works:

Step 1: Introduce what scientists call “misinformation”, by telling a person they did something they didn’t. This will be more convincing if you have authority and claim to have evidence.

Step 2: When they dispute your accusation, saying something like I didn’t do that, refute it. Of course you did. Just tell the truth.

Step 3: Offer to help them remember. Get them to imagine what the crime could have been like. This leads to something called “imagination inflation,”,where picturing things happening forms the foundation for a belief they actually did happen.