Naomi Sanders was making steak for dinner.

Vallejo police know this because, when they searched her apartment the day after she was murdered, it was still waiting half-cooked on the stovetop. It was a double portion; police think the second steak was for her poodle Cindy.

Sanders, 57, lived alone in Apt. 12 of the Oakwood Garden Apartments at 1077 Oakwood Ave. Sometime during the night of Feb. 27, 1973, someone came in and attacked her. Police found her partially nude body on her bed; the murderer had raped and strangled her. Cindy watched over her owner’s body until police took her away.

Police knew immediately it would be tough to find leads in the case. In Sanders’ window was a large cardboard sign with the word “OPEN” written on it. She was the apartment building manager, and regularly invited apartment-hunters in. With no known enemies or angry ex-boyfriends, police figured their suspect crossed paths with Sanders this way.

Months turned to years, then decades. For 47 years, as Sanders’ friends and family too passed away, her murder went cold.

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In 2014, the Vallejo Police Department submitted Sanders’ clothing from the crime scene to the California Department of Justice laboratory. Lab techs discovered a semen sample and developed a DNA profile of the suspect. But when police entered it into the nationwide DNA indexing system CODIS, no matches were found.

They tried again a few years later to no avail. But in 2018, detectives partnered with Parabon NanoLabs, a genetic genealogy company. Like other similar companies in the news, Parabon NanoLabs uses samples provided by police and compares them to known profiles from users who submitted their DNA using commercial genealogy kits.

The search turned up two leads. Detectives went to Louisiana to follow one up, but it was a dead end. The other led them to a man who appeared to share genetic similarities to their suspect. The man agreed to submit his DNA and, after testing, police finally had their match.

Last week, Vallejo police announced they believe Sanders was killed by that man’s father, Robert Dale Edwards. Edwards was 22 at the time of Sanders’ murder, and detectives learned he had a connection to her: His father was once her co-worker.

Edwards had a long criminal history. Over two decades, police say he racked up charges for assault, theft, DUI, domestic violence, assault with a deadly weapon, and attempted murder. Edwards died of a drug overdose in Napa County in 1993.

Sanders had no children so, when detectives recently sought out family, they found the children of her nine siblings. Two nieces, Sharron and Dixie, issued a statement on behalf of the family.

“As you can imagine, over that 46 years, many family members directly affected by the loss of Naomi have also passed, and, unfortunately, they cannot be afforded the truth as to what happened,” it reads.

“Those of us who do remember the stories of Naomi’s life and untimely death can now feel closure thanks to the determination and teamwork of the Vallejo Police Department and partnering law enforcement agencies. May Naomi now rest in peace.”

Katie Dowd is an SFGATE Senior Digital Editor. Contact: katie.dowd@sfgate.com | Twitter: @katiedowd