At a hearing last year, an FBI agent testified that Richards planned to expose the 5-year-old to sex acts to "see it's an enjoyable thing."
Investigators say the couple had been in contact with a purported buyer who turned out to be an FBI informant.
Block is accused of offering to sell a child and distributing child pornography. He is set to stand trial in May. His attorney has said that Block took no part in what's alleged.
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