Deadly Assassin

was able to dispel the Fourth Doctor's belief that he was the Deadly Assassin by producing multiple Time Lord eyewitnesses that confirmed his whereabouts at the time of the assassination, one of whom proudly held up a severed leg, another the Master's severed arm and yet another a lone ear. (NOTVALID: Doctor Who? 187)

Behind the scenes
In the television story The Deadly Assassin, Chancellor Goth, acting under orders from the Master, was the titular assassin.