Toronto Mayor Rob Ford wrote a character reference letter for Alessandro Lisi, praising a man convicted of threatening to kill a former girlfriend.

In the letter, ordered released Tuesday by an Ontario Superior Court judge, the mayor noted Mr. Lisi was "an exemplary member" of Mr. Ford's 2010 election campaign team and demonstrated "tact and diplomacy."

"I have known Mr. Lisi for several years, and he has always conducted himself in a courteous and polite manner," Mr. Ford stated in the one-page note dated June 4, 2013, and printed on the mayor's official City of Toronto letterhead.

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The mayor defended his letter writing at City Hall on Tuesday afternoon, noting he pens a lot of letters: "I support a lot of people." Mr. Lisi was recently charged with drug offences, including trafficking in marijuana.

Other municipal politicians, however, said they're cautious about writing character reference letters. Councillor Adam Vaughan contended it's inappropriate for elected officials to interfere in legal proceedings.

Federally, politicians are not allowed to send reference letters to courts and regulatory tribunals. Conservative MP John Duncan resigned from his cabinet position earlier this year after he sent a character reference letter to a federal Tax Court judge on behalf of a constituent.

In Toronto, the rules are less clear, said John Mascarin, a municipal law expert with Aird and Berlis LLP. The code of conduct for council warns members against improperly using the influence of their office, but it does not specifically touch on reference letters. Still, the fact Mr. Ford used official letterhead could be problematic, Mr. Mascarin said.

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Mr. Ford has faced persistent questions about the people he surrounds himself with since reports emerged in May of a video of the mayor purportedly smoking crack cocaine. The alleged video has not surfaced publicly. Mr. Ford has denied using crack cocaine and has publicly questioned the video's existence.

But sources close to the mayor's office have told The Globe and Mail that Toronto police have interviewed at least five former staffers in the mayor's office about attempts by people to retrieve the alleged video. Some of the questions police asked, according to the sources, focused on Mr. Lisi, a regular late-night companion of the mayor who was known to drive him to events.

Mr. Lisi, 35, has a long history of drug dealing in central Etobicoke, according to seven sources interviewed by The Globe, who said they've either purchased marijuana or cocaine from Mr. Lisi or witnessed him supplying people with illegal drugs. Toronto police arrested Mr. Lisi on drug and conspiracy charges on Oct. 1. At the time, the mayor said he was surprised by the charges and called him "a good guy."

Deputy Mayor Norm Kelly called the letter about Mr. Lisi "innocuous," while Councillor Doug Ford characterized the letter as one of many written by his brother to help individuals who get into trouble with the law.

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"He doesn't judge people when they come to him," the councillor said. "He doesn't throw the book at them. He tries to help them."

The mayor's letter in support of Mr. Lisi was one of several court exhibits released Tuesday as a result of an application from The Toronto Star. The documents are connected to Mr. Lisi's 2013 trial on six criminal charges, including assault, harassment and forcible confinement.

A judge dismissed five of the charges, but convicted Mr. Lisi of threatening death against an ex-girlfriend. He received a suspended sentence and two years of probation. Mr. Lisi is appealing the conviction.

Among the documents released was a partly censored presentence report on Mr. Lisi's case. The report, dated June 10, 2013, was prepared by a provincial probation and parole officer. Mr. Lisi, a high-school dropout, told the officer his future plans included working for the City of Toronto "with the endorsement of his 'close friend,' Mayor Robert Ford."

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This is not the first time Mr. Ford has spoken out on behalf of an associate facing a criminal prosecution. Last year, Mr. Ford wrote a character reference for another man with a criminal past, Douglas Sedgewick. In a letter composed on City of Toronto letterhead, Mr. Ford stated he knew Mr. Sedgewick "through my role as an elected official active in the community" and that Mr. Sedgewick "has always conducted himself in a courteous and polite manner."

Mr. Sedgewick, who was convicted of murder in the 1980s, submitted the mayor's letter to a municipal licensing hearing considering whether to reinstate his towing licence. His licence was reinstated with conditions.