King of crime Michael Connelly is convinced these notorious unsolved murders are linked

When he was a young crime reporter for The Los Angeles Times , Michael Connelly admired the detectives who worked a case even after it had gone colder than yesterday’s coffee. The ones who were “undaunted and relentless”, as he recently put it, restless and patient at the same time. It’s the quality that makes Harry Bosch, the detective Connelly created, such a memorable character.

“A city that forgets its murder victims is a city lost,” a captain tells Bosch in one of Connelly’s novels. Real cops he came to know liked that saying so much, they turned it into a sign at the cold case unit at the Los Angeles Police Department headquarters. When the office moved a few years ago, they gave the sign to Connelly.

“There’s this emptiness that comes from knowing that people get away with it,” Connelly said. He’s written more than 40 novels, sold 90 million books. His writing room is decorated with posters of stars who’ve played his characters: Titus Welliver as Bosch. Matthew McConaughey as Mickey Haller. Maggie Q as Renée Ballard.

The late nights at the Short Stop, the legendary Echo Park cop bar, are long gone; Connelly lives in the Hollywood Hills now. But what was true then remains true today. A murder unsolved is a city unmoored.

So when two of Connelly’s most trusted collaborators – retired LAPD detectives Rick Jackson (partly the basis for Bosch) and Mitzi Roberts (the inspiration for Ballard) – came to him early last year with the claim that an amateur sleuth in West Virginia had solved the most notorious murder in LA history, there was only one thing Connelly could do: work the case as if he were still a young reporter ravenous for the big scoop.

That investigation resulted in Killer in the Code , a podcast whose second season has returned with the first two episodes of six. The 10-episode first season roiled the true-crime community by arguing that a World War II veteran named Marvin Margolis was responsible for two of the most famous unsolved crimes in California history: the 1947 Los Angeles murder of Elizabeth Short, immortalised as the Black Dahlia, and the five killings committed by the Zodiac throughout the San Francisco Bay Area in the late 1960s.

“I have no doubts,” Connelly said in the run-up to the second season, which focuses on advancing the case against Margolis as if he were still alive. The evidence pointing to Margolis as the killer, Connelly added, was “completely convincing”.

Margolis has been floated before as a suspect in the Short killing, but he has never been previously connected with the Zodiac killings. The podcast has infuriated many in the true-crime community. Connelly is viewed by some as out of his depth, duped by bad cryptography and shoddy evidence.

“Mike was a fine reporter, but those reporting days are in the rearview mirror,” said Larry Harnisch, a leading Black Dahlia expert who has led the opposition to Killer in the Code .

Connelly, now 70, admits that when he first got involved in the podcast, he did not think it would become something of a second job.