XENIA, Ohio -- Police investigations of potential sexual predators on the Internet are coming under fire from defense lawyers.

Xenia police pioneered child exploitation investigations several years ago, but now arrests made by officers they helped train are being questioned.

Xenia police have made more than 50 sex-related arrests in the last 3-4 years based on Internet investigations.

Detectives also conducted seminars for dozens of other police departments in Ohio and around the country, but now some defense lawyers are questioning whether there's even really a victim in these cases.

Winter, spring, summer and fall, Xenia police have followed potential sexual predators in them all.

To date, more than 50 arrests have been made of men trying to meet minors for sex and their official charge is importuning.

The evidence against them was gathered by means of Internet chats where the men believed they were talking to 14 and 15-year-old girls.

Xenia detectives pioneered the technique of posing as young girls to find would-be predators and they trained officers from many other departments including Cincinnati and Hamilton County.

Now, defense lawyers there like Louis Sirkin is criticizing the technique, saying "in a free society it's very dangerous to try and control thought".

Sirkin says when a detective poses as a teenager, there is no victim.

Xenia detectives say they believe these men would all commit a sex crime if they were actually meeting a teenager, and say most of the men come prepared with anything from condoms to Viagra.

Authorities in Xenia say they don't plan to stop what they call protection of children.

Xenia police say most of the men they've arrested plead guilty quickly to charges of importuning and a few have tried unsuccessfully to fight the charges on grounds of entrapment.

Now, the lawyers in Cincinnati are trying to challenge the constitutionality of the law, so far unsuccessfully.