Sidney "Sid" Leithman (14 October 1936 – 13 May 1991) was a Canadian lawyer known for representing numerous reputed organized crime figures in Montreal, Quebec.

[1] Leithman had a reputation as an intelligent and aggressive lawyer known for winning his cases, or at least greatly reducing the sentences imposed on the accused even if they were convicted.

[1] The Canadian author Robert Knuckle wrote that Leithman was a "stylishly-dressed McGill graduate with an effusive personality" who was "well known as a wheeler-dealer among the political and commercial leaders of the city.

"[4] On 18 February 1971, Leithman hosted a press conference where his client, crime boss Frank Cotroni, spoke about his arrest in Mexico the previous month.

[1] In November 1975, Leithman, together with fellow lawyer Rolland Blais, held a press conference in which their clients, the Dubois brothers, stripped naked in front of the assembled reporters to support their claims that police had beaten them.

[9] Savard denies the "execution" claim and argues that it was illogical for him to kill Slawvey, as he wanted him alive in order to pressure him to turn Crown's evidence against Ryan.

[1] In 1983, Leithman was hired as the defense lawyer for Jair "El Mocho" Garcia, the Montreal agent for the Cali Cartel, and an associate of Ross'.

[12] As part of his work, Leithman had befriended Claude Savoie, the chief of the Royal Canadian Mounted Police (RCMP)'s national anti-drug squad.

[11] Leithman served as the conduit, taking briefcases full of CA$200,000 in cash to Savoie in exchange for information about what the RCMP knew about the West End Gang.

[14] He liked to work early and that day he was preparing to make his final arguments in a case concerned several Colombian men accused of drug smuggling.

[14] At 6:48 am, at the intersection of Rockland Road and Monmouth Avenue, a car that was waiting for him suddenly pulled out onto the street, forcing Leithman to stop.

[18] By contrast, Canadian journalist D'Arcy O'Connor wrote that on the basis of interviews with various Mounties that Leithman was killed by one of his Colombian clients for reasons that remain unknown.