Scott Peterson

They were once lovers, but now Amber Frey and Scott Peterson are on opposing sides — he's standing trial for the murder of his pregnant wife, Laci, and she's the prosecution's star witness. Frey believed Peterson was single, but when she learned he was married following the Dec. 24, 2002, disappearance of Laci Peterson, she contacted police and agreed to play along with Peterson's charade, all while taping their phone conversations.

The single mother from Fresno isn't the first to take the stand against a former love or sex interest. Courttv.com takes a look at defendants faced with damaging testimony offered up by the men or women from their pasts.

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