A home improvement contractor accused of bilking an elderly Georgetown widow of more than $200,000 for repairs valued at less than $3,500 was sentenced yesterday to a stiff prison term by a judge who noted that the man had a "record of preying on old people and helpless people."

Prosecutors said that the case was the largest home improvement fraud on record in the District of Columbia.

"The character of the crime assumes an almost uniquely despicable" element, D.C. Superior Court Judge Truman A. Morrison III told the defendant, Michael Patrick Dowling, 29, of Lowell, Mass.

Dowling's victim, Agnes Pearson, 86, leaned forward in her courtroom seat as the judge sentenced Dowling to three to 10 years in prison -- a few months short of the maximum -- and noted that Dowling already is serving an out-of-state prison term for a similar offense.

"There are numerous jurisidictions waiting to get their hands on Mr. Dowling" in similar cases, the judge said, adding that he would not order restitution because Dowling probably lacks the "ability to pay" as a result of the substantial prison terms he faces and because Pearson is of an "advanced age" without any known family.

"He was very slick. He knew just what to say at the right time,"Pearson said in a witness room outside the courtroom, as she described how Dowling first approached her about performing a minor roof repair and then over a 10-month period had her accompany him to her bank to endorse checks.

"Unfortunately," she added, "his work is not like his tongue."

U.S. Attorney Joseph E. diGenova called the case "the largest home improvement scam" in the District and described Dowling as a "predator."

DiGenova said that the grand jury is investigating other people who may have been working with Dowling.

In a sentencing memorandum filed with the court, prosecutor John P. Dominguez described how a door-to-door inquiry from Dowling and his coworkers to fix Pearson's roof for $5,765 eventually grew to $213,000 because Dowling was always "finding more items to repair around her home just before finishing the previous job."

Dominguez said that the payments included money for replacing pipes and digging up the street to install a new water main, work that in reality included only repainting the pipes and never replacing the water main.

Pearson, a former teacher who has no known living relatives and lives alone, was "vulnerable in an almost childlike manner" when she met Dowling, Dominguez said, describing how Pearson is frail and at times appears confused.

Pearson's plight came to the attention of D.C. police as WJLA-TV (Channel 7) began preparing a news story about her problems.

"He was really very likeable at times," Pearson said of Dowling, "but I don't think he was very nice."