Story highlights Syed has been serving a life sentence in the slaying of his ex-girlfriend

The first season of "Serial" focused on Syed's case

(CNN) The Maryland Attorney General's office is appealing a new trial granted to Adnan Syed, whose murder conviction was the focus of the first season of the popular "Serial" podcast.

In the appeal on Monday, Attorney General Brian Frosh's office urged Baltimore Judge Martin Welch to "review, and reverse, the post-conviction court's ruling that Syed's trial attorney was constitutionally ineffective in her cross-examination of the state's cellphone evidence."

Syed's post-conviction lawyer, C. Justin Brown, confirmed the news on Twitter.

State filed an appeal today in Syed case. We will start dissecting it tomorrow. #freeAdnan — Justin Brown (@CJBrownLaw) August 2, 2016

The judge vacated Syed's conviction and ordered a new trial for Syed, based on claims that the defendant's trial lawyer failed to cross-examine an expert witness about the reliability of cell tower location evidence.

Syed, 35, was convicted in 2000 and sentenced to life in prison on murder and kidnapping charges in the slaying of his ex-girlfriend, Hae Min Lee. Her strangled body was found in a shallow grave in a park one month after she went missing in January 1999.

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