Lawyers for Adnan Syed, who is serving life in prison after being found guilty of killing his ex-girlfriend in 1999, were finally able to take the first step Monday in getting his conviction overturned.

Syed's saga of high school love — and a killing he has always denied having anything to do with — was the subject of the immensely popular podcast "Serial." His lawyers filed a brief with the Maryland Court of Special Appeals, which agreed to hear arguments after two previous attempts to appeal the verdict were denied.

The road to the appeal has been a long one. Syed, 34, was sentenced to life in prison plus 30 years in 2000, after one mistrial, for the murder of his former girlfriend, Hae Min Lee. The appeal wasn't granted until last month.

And the road ahead could also be lengthy. The brief requests a new trial — and Chief Appeals Judge Peter B. Krauser hasn't set oral arguments on whether to open one until June.

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Syed's lawyers, Justin Brown and Kasha Lesse, contend that their client was "denied the right to 'decide his own fate,'" because his late lawyer, Christina Gutierrez, never requested a plea deal — and lied about it, telling Syed she had.

Brown and Lesse also argued that Gutierrez never contacted the only known person who could potentially provide Syed with an alibi — and lied about it, telling Syed she had.

The witness, Asia McClain, had written Syed letters in 1999 that said she was in a library with him at the time of the murders, and Syed asked Gutierrez to pursue the claim. Gutierrez told Syed that she "'looked into it and nothing came of it,'" according to the brief, but McClain wrote an affidavit in 2000 that stated that no attorney had ever contacted her.

The brief said Gutierrez, who was disbarred in 2001 and died in 2004, "effectively stopped representing" Syed.

"The errors committed by trial counsel were of such a fundamental nature that Syed must be given a new trial," his lawyers argued in the brief.

The brief also said the testimony of Jay Wilds, a witness the "state relied heavily on … was riddled with inconsistencies."

Prosecutors argued that Syed was devastated when Lee broke up with him, since he had dishonored his Muslim family to be with her, which motivated him to kill her. Wilds testified that he was with Syed when he buried her body in a Baltimore park, but "police interviewed him three separate times, and each time he told a different story," the brief said.

A spokesman for the Maryland Attorney General's Office, which is prosecuting the case, told NBC News that it had no response to Monday's filing.