A Vancouver woman unknowingly provided critical DNA information that led police to arrest a distant relative in a 39-year-old homicide case in Iowa.

Brandy Jennings said her parents divorced when she was young, and she barely knew her father. Years after his death in 2009, she decided to try to find out more about his side of the family.

Jennings’ mother purchased a DNA kit for her through Ancestry.com. She spit into the collection tube and mailed her saliva sample in May 2018. Once she received her results, she uploaded them to a public database, GEDmatch.com, and promptly forgot about it — until last week.

That’s when she started getting notifications through Facebook asking if she were related to a Manchester, Iowa, man police arrested in December on suspicion of first-degree murder.

“I’m like, ‘No, not that I know of,’ ” Jennings said.

Police arrested 65-year-old Jerry Lynn Burns after a DNA sample connected him to the December 1979 killing of Michelle Martinko outside a J.C. Penney’s store in Cedar Rapids, Iowa. Martinko, an 18-year-old high school student, suffered 21 stab wounds, as well as defensive wounds to her hands consistent with a struggle inside her family’s car outside the store.