Brendan Dassey was 17 years old when he was convicted of helping his uncle murder and sexually assault Teresa Halbach, a photographer, in a Wisconsin salvage yard. He was 26 when the Netflix series “Making a Murderer” made that case — and the concerns about how it was handled — a global sensation.

Now, weeks from his 30th birthday , Mr. Dassey, who has pursued several failed legal appeals, is seeking mercy once again: On Wednesday, his legal team launched a campaign to persuade the state’s governor, Tony Evers, a Democrat, to grant him clemency.

The effort includes Mr. Dassey’s first audio interview, recorded for a podcast about wrongful convictions, as well as television and print media exclusives. His legal team is also holding a news conference in Madison, Wis., featuring educators, a clemency expert and a former United States solicitor general who is now part of his legal team.

“It’s really a coalition of voices that are calling on the governor just to take a close review of this case — watch the videotapes, read the records,” said Laura Nirider, one of Mr. Dassey’s lawyers and a co-director of the Center on Wrongful Convictions at Northwestern University’s law school in Chicago.