Lieutenant Calley asked Latimer in mid-1969 to defend him against charges growing out of his role in the massacre at My Lai. Calley used his life savings of $6000 to retain the elderly lawyer. Although prior to defending Calley, Latimer had enjoyed a distinguished career, it was an unwise choice by Calley. Although Latimer seems to have felt a personal connection to his most famous client stating, “Why, he could have been my son ... you couldn’t ask for a nicer boy,” most observers felt Latimer "was past his prime and was a dubious choice for an arduous case.” Latimer was 70, poor of hearing, and asked questions that were rambling and hard to follow. His defense rested on an incoherent mixture of following orders of a superior, outright denial of specific acts, a portrayal of Calley as the victim of a war gone bad, diminished capacity brought on by marijuana use, and blame shifting to those lower in the chain of command (especially Paul Meadlo). The defense was ineffective, and the jury returned a verdict of guilty.
Prior to defending Calley, Latimer had served as Utah Supreme Court judge, a former Military Court of Appeals judge, a member of the Utah State Board of Pardons, and a practicing attorney in Salt Lake City. When first approached by Calley, Latimer was involved in defending one of the eight green berets in connection with another murder charge.