BALTIMORE (WJZ) — Adnan Syed’s defense lawyers have filed an amicus brief at the United States Supreme Court regarding his case.

Syed, whose murder conviction is chronicled in the hit “Serial” podcast about the killing of his ex-girlfriend Hae Min Lee, has attempted to have his conviction reconsidered before.

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He was denied a new trial earlier this year, when the Maryland State Court of Appeals voted 4-3 that there was “not enough” to overturn Syed’s conviction.

His defense is claiming that Syed was not given a proper opportunity to “investigate an unbiased and credible witness,” aka, Asia McClain, who claims she can vouch for Syed’s whereabouts during the murder of his ex-girlfriend Hae Min Lee.

In the brief, the defense group claimed that the Maryland Court of Appeals’ decision to deny Syed a new trial and reinstate his conviction “will impact criminal defendants and, in particular, habeas petitioners, far beyond Maryland’s borders,” citing cases throughout the country.

“It has consequences not only for Syed, but for all defendants with counsel who fail to investigate and present testimony from a neutral, credible alibi witness,” the brief read., “If this outlier decision stands, it will frustrate the ability of courts around the country to remedy trial counsel’s prejudicial errors,”

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Syed was convicted in February 2000 of killing his high school ex-girlfriend Hae Min Lee. Lee, who was 17 at the time, disappeared on Jan. 13, 1999.

Her body was found several weeks later in Leakin Park. An autopsy report stated Lee had died from manual strangulation.

At the time Syed and Lee were students at Woodlawn High School in Baltimore County, Maryland.

Syed was found guilty of first-degree murder and sentenced to life in prison.

Now, his lawyers are hoping the U.S. Supreme Court will free him.

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This story is developing.