I haven't watched it in a while, so I may get some specifics wrong, but it goes through various hypotheticals, until finally getting to the point where you are innocent, and you only tell the truth, but talking to the police gets you convicted. IIRC the example was you saying "I was out of town visiting my mom when the crime happened" but they have a (mistaken) witness putting you near the scene. The fact that you (supposedly) lied about where you were combined with other circumstantial evidence may be enough to convict you.

Note also that even an innocent person will almost always give contradicting accounts of a situation if interrogated for long enough.

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There were several such examples, including the one I remembered from 14-23 minutes.