SALISBURY – A Salisbury man is behind bars on $500,000 bail over an alleged scheme that went on for years and involved a number of unsuspecting women victims.

Police say that David Anderson, 44, had placed ads on Craigslist and distributed fliers around Salisbury offering $25 to $50 to women willing to participate in clinical research.

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“I’m not an expert but I would speculate he’s got some issues,” says Salisbury Police Chief Tom Fowler.

Anderson told the women who responded that they were required to undergo an initial examination, which he performed, that required invasive digital probing and other personal acts, police said.

“It was pretty invasive and disturbing,” says Chief Fowler. “I’ll leave it at that.”

To appear convincing, investigators say Anderson purchased a number of medical devices and set them up in his home.

Anderson is accused of secretly videotaping those encounters.

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So far, thousands of images have been recovered and 20 victims have been identified, according to authorities.

Police say Anderson, in an effort to appear legitimate, had each victim fill out questionnaires. Investigators used the questionnaires that Anderson kept to identify the victims.

Authorities suspect there could be many more victims.

They believe the alleged scheme went on for several years, and confirm that along with Massachusetts and Connecticut authorities, investigators in New Hampshire, New Jersey, New York and Washington are investigating similar allegations.

Anderson is also accused of secretly videotaping pre-teen relatives. The allegations came to light after Anderson was arrested in Connecticut and charged with possession of child pornography.

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Court documents say his estranged wife tipped off police.