Walter Flint is a serial killer responsible for the rapes and murders of at least five women and girls. His ex-wife, Allison Ashburn, was pregnant with their son Danny by the time he was imprisoned.
Allison killed Danny to leave him behind and start a new family with her husband John. Flint's DNA was a familial match to Danny; upon being interrogated, he directed investigators to Allison's new family. (L&O: "Choice of Evils")