NEW LONDON - Hours after a prosecutor dropped violation of probation charges against convicted serial rapist David Pollitt that were based on a faulty GPS reading, judicial officials said they'd investigate the reliability of the monitoring system for which the state pays a contractor nearly $1 million a year.

Pollitt, 55, was arrested Wednesday on charges that he violated the terms of his probation. Pollitt has been staying with his sister in Southbury since his release from prison last fall. He had been convicted in a series of sexual assaults and had to wear a GPS monitoring device on his right ankle as a condition of his release.

After his arrest Wednesday, Pollitt's family paid about $7,500 to a bail bondsman to post $100,000 bail. Pollitt was released until a court appearance Friday in New London.

That's where New London State's Attorney Michael Regan told Judge Susan B. Handy the arrest warrant was based on faulty data from the contractor that provides GPS monitoring services to the state.

"The GPS system was not functioning properly at the time [of] the reading," Regan said. "In light of what probation has stated to me, I'm going to withdraw that warrant."

Judicial officials will conduct an "internal review" of what went wrong, how it can be avoided, and, perhaps, whether the state should stick with the current contractor, said William H. Carbone, judicial branch director of court support services.

Carbone said officials had never before based a probation-violation charge solely on GPS readings. He said officials believe the GPS system is reliable, but "not perfect," just as cellphones, which sometimes lose their signal, also are imperfect. GPS is "only one tool" for probation officials, who use it to monitor 30 to 40 sex offenders, he said.

"We would not have pursued the violation of probation warrant with that information," added Keith Furniss, a Waterbury probation office supervisor. He said the warrant relied exclusively on the GPS data, and there were no witnesses to Pollitt's now-discounted departure from his sister's property.

Authorities had charged that Pollitt left his sister's property for 15 minutes on Sept. 3. Probation officials relied on verbal confirmation from Pro Tech Monitoring Inc. of Odessa, Fla. - the subcontractor that provides GPS monitoring services to probation authorities - when the arrest warrant was drafted. A day after the warrant was signed by a judge and served on Pollitt, probation officials learned from the contractor that the data they relied on was unreliable, Regan said.

Handy - who had ignored pressure by Gov. M. Jodi Rell and Attorney General Richard Blumenthal last fall to keep Pollitt in prison even though he'd completed his 24-year sentence - sent Pollitt on his way, admonishing him to still comply with probation conditions.

Leaving court, Pollitt, who denied leaving his sister's yard, quipped to an official, "Kind of embarrassing, isn't it?"

Outside court, Pollitt's lawyer, Ioannis A. Kaloidis, lashed out at state officials who he said "rushed to judgment" and reignited the "lynch mob mentality" that greeted Pollitt upon his arrival in Southbury. He cited comments Rell had made Thursday in which she expressed "concern" that a week elapsed from the time of the alleged violation until Pollitt's arrest. "Had they waited one more day they would have gotten to the bottom of this."

Kaloidis expressed surprise that officials were unaware of problems with GPS and other monitoring devices. He said Pollitt had kept a log of at least 44 false alerts and sometimes was awoken at night by a call from probation officials saying his device indicated he was away from his sister's house.

Thomas J. Ullman, Connecticut Criminal Defense Lawyers Association president, cited "numerous cases ... where the electronic monitoring devices have been mistaken."

On Friday, the co-chairmen of the state legislature's judiciary committee, Sen. Andrew J. McDonald and Rep. Michael Lawlor, said the GPS system "has reportedly been malfunctioning for what appears to be an extended period of time."

Blumenthal called for an investigation into the GPS system that Pro Tech provides as a subcontractor to California-based G4S Justice Services Inc., which has a $950,000-a-year contract with the judicial branch for electronic monitoring of probationers and parolees. "There is simply no excuse for this malfunction," he said.

Rell released a statement saying, "This incident raises a number of troubling questions: Is the GPS system we are using reliable? Can we be sure this will not happen again?"

A Pro Tech executive wrote Thursday to G4S - apologizing for "any embarrassment ... this has caused the Connecticut Judicial Branch," and saying re-examination of the initial GPS readings showed that "based on environmental conditions [and] GPS signal strength," the company "could not clearly state that [Pollitt] had left the residence."

Parole officials use GPS tracking - under the same contract with G4S - to track about 200 offenders in the community, some convicted of sex crimes and others on serious burglary charges.

Contact David Owens at dowens@courant.com.

Copyright 2008, The Hartford Courant