WALPOLE, N.H. (AP) – This small town’s police department is getting help from a national volunteer group to arrest alleged online child sex predators. Walpole’s police department has one chief, two full-time and seven part-time officers.

Det. Richard Westney, a part-time member of the force, says without help from the group, Perverted Justice, it would be difficult for Walpole police to invest the time needed to engage predators online.

“For every one we catch there may be 10 or 20 more that we don’t learn about,” Westney said.

Perverted Justice trains volunteers to impersonate children in online chat rooms. The group started working with Walpole Police last year. Since December, they’ve helped police arrest two from New Hampshire men and one from Vermont.

In all the cases, police said the men believed their online targets were underage girls and agreed to meet them in Walpole. When the men arrived for their meetings, they were met by police, not young girls.

The first arrest was of 39-year-old Christopher McGuire, of Peterborough. Perverted Justice volunteers contacted Westney on Dec. 26, 2006, with information about McGuire. Police said Perverted Justice provided transcripts of conversations, photos and pornographic video McGuire allegedly sent to a girl he believed was 13 years old. He is now awaiting trial on a charge of attempted sexual assault.

Police next arrested Andrew Kessen, 21, of Brattleboro, Vt. He also was charged with attempted sexual assault and his case goes before a Cheshire County grand jury later this month.

Police said the third arrest, of 46-year-old John Trant Jr., of Hudson, was the strangest.

Authorities said Trant started his online relationship with a 13-year-old “girl” by sending fatherly advice and a video of himself eating birthday cake, then began transmitting pornographic photos of himself.

When police arrested Trant several weeks ago, they said he claimed he arranged the meeting to warn the girl to be careful of chatting with strangers online. Police said they found condoms and birthday cake in Trant’s pickup truck. He is scheduled for a court hearing in May.