One of the last surviving members of the Manhattan’s notorious Westies gang has died in a Californian prison.

James "Jimmy Mac" McElroy was serving a 60-year sentence for racketeering when he passed away last week, sources told the New York Post.

The 60-year-old was most well known as the key witness in one of the many failed prosecutions against John "Teflon Don" Gotti.

The crime lord took stage at Gotti’s 1990 trial for allegedly the assassination of a union official, testifying that the man the Westues boss had asked him to take the man out at Gotti’s request.

"Jimmy [Coonan] said they wanted someone whacked," McElroy testified, explaining that when he asked who "they" was, Coonan said, "John Gotti."

The hit failed when McElroy and three other union officials shot union official John O’Connor four times in the buttocks and legs.

After his testimony, McElroy remained behind bars for his 1986 racketeering conviction.

‘Jimmy Mac’ McElroy