Before joining Red Shield, David was the sole survivor of a chiropteran attack on his special forces squad. His father was also a member of Red Shield and was one of Saya's victims in the Vietnam incident. It is implied that he, along with Joel, are the only members that are descended from a line of Red Shield operatives. He is aware of Saya's past life and wishes to use her in the struggle against the chiroptera. David's red crystal item is a cross.
David tends to be straight-faced and serious, with a cold personality. However, he also assumes an unofficial guardianship of Kai and Riku, and would be instrumental in helping Kai come to terms with what Saya is and with Riku's conversion to a chevalier. He seems to take a particular interest in helping Kai grow up to be a strong man who can support Saya and Riku as their brother, despite their unusual natures.
When the Red Shield's headquarters are destroyed and Saya is believed to have gone down with it, David sinks into a deep depression and becomes an alcoholic. Kai helps him get back on his feet, though, and he returns to his duties slightly more cheerful and able to smile than he had been before.
During the investigations into one of Cinq Flèches's lab, he finds Julia and she tells him something about the research they are doing. He talks to her briefly again at Amshel's party, and lets her know that she will always be welcome back with the group.
Towards the end of the series, Dr. Collins tries to murder Julia, but David protects her, getting critically wounded himself. Julia keeps vigil over him in the hospital, and after he recovers they begin a romantic relationship.
At the end of the series, Julia is pregnant with his child.