David "Legal" Siegel (b. 1932) is a resident of Menorah Manor in Los Angeles, and a former law partner of J. Michael Haller. He is the father of two sons. He is described as a brilliant legal strategist. He reportedly sent the younger Haller to law school after his father died, but it is not clear what this means. Did he simply help him gain admission or did he help pay for his education? In any case, Haller views Siegel as a substitute father.
When he retired and at the time he moved into Menorah Manor, Siegel placed a phony obituary for himself in the California Bar Journal so that any disgruntled former clients wouldn't bother looking for him. It was so effective that very few people aside from Haller knew that Siegel was still alive. Haller would often visit Siegel to seek legal advice and to bring him food that he was not supposed to have in Menorah Manor, such as a French Dip sandwich from Phillipe the Original.
In November 2012, Mickey Haller visited Siegel after his client killed two pedestrians while driving drunk, leading to him losing the election for District Attorney and having his daughter turn against him. Siegel told him not to feel bad because he was simply doing his job. Haller did not find any comfort in this response.
In 1988 Siegel represented Preston Borders' in his trial for the murder of Danielle Skyler. In 2017, when it appeared that Borders' conviction might be voided, Siegel was visited by Mickey Haller who was assisting Harry Bosch. Siegel reported that Borders wanted to testify in his own defense, against Siegel's advice. Borders' testimony was not believed by the jury, leading to his conviction. Siegel said Borders was the only one of his clients that ended up on Death Row. Siegel's statements about the handling of Borders' case in 1988 helped Haller and Bosch in their efforts to keep Borders behind bars.