Noah Bunning was the college boyfriend of FBI Agent Dana Lewis, having an on-again, off-again relationship with her. Though Bunning got over her, Lewis didn't get over him. Lewis wanted to keep them together when she revealed he impregnated her, but Bunning made her have an abortion, which devastated Lewis.
When Bunning started dating Kira Stanger, she ended up pregnant too. However, Bunning decided to step up and marry her to raise their baby. Lewis tried to warn Kira, but Kira told her about their engagement, leading to Lewis strangling Kira in a rage. The case went cold, as Lewis framed an at-large serial killer, Brian Traymor, by staging the scene accordingly.
25 years later, Traymor was caught, but Kira's parents knew she'd never let her guard down in front of a stranger. Noah was questioned about their relationship, and he revealed Kira's pregnancy. When Lewis' former romance with him and her eventual abortion were found out, she was interrogated and eventually confessed to murdering Kira. Lewis was arrested and imprisoned, finally closing the investigation. (SVU: "Secrets Exhumed")