Conrad Murray has broken his silence about NOT testifying in the Michael Jackson wrongful death trial ... and he did it by SINGING on live TV.
Murray -- who is serving a 4-year sentence for killing MJ -- called into "Anderson Cooper 360" moments ago from jail. At first he sang the same old tune ... insisting he was innocent and in the process of appealing the case.
But then he did something really, really weird -- belting out his version of "The Little Boy That Santa Claus Forgot" (better sung by Nat King Cole)!
Murray seemed to be explaining how much he and MJ had in common ... and why he's chosen to plead the 5th in Katherine Jackson's $40 billion suit against AEG -- but you gotta watch it, because his singing is super awkward ... and awful.