A judge will decide whether to grant a new trial to the Alamo man who was convicted of killing a Donna teen.

Lawyers for Carlos Julian Contreras argued the trial was mishandled.

Contreras was sentenced to 60 years in prison in September after he was found guilty in the shooting death of 18-year-old Genaro Isaiah "Izzy" Castillo. Castillo’s body was found near Donna Lake in January 2020 after he was shot multiple times.

As previously reported, a mistrial was initially declared on Sept. 12 after the defense team learned that prosecutors offered immunity to Contreras’ common-law-wife — Miranda Luna — without disclosing it.

PREVIOUS COVERAGE: Attorneys for man convicted of killing Donna teen seeking new trial

On the stand, Luna said she witnessed Contreras shoot Castillo after he was forced to do so by a man identified as Jorge Veliz, who was never charged in connection with the shooting.

The filing called Luna’s testimony “false” and “misleading.”

Testimony from Monday’s hearing centered on how prosecutors handled the immunity deal made with Luna.

Lead prosecutor Gabriella Guerena testified that she spoke with Luna in early September, and said an immunity deal was negotiated between Luna’s attorney and the District Attorney’s office.

The defense said the timing raises red flags because that's when Luna reportedly gave prosecutors a new statement that both sides said contradicted her original witness interview.

The defense brought up statements made during trial, where the state told the jury in opening statements that Luna might "lie"

The defense argued the state knew Luna’s testimony was unreliable, but still went forward with the immunity deal and put her on the stand anyway.

“The fact that there was an immunity agreement that required her to testify, the fact that they told the jury up front she was gonna lie, and the fact that they argued in the trial that she lied, all of that is presentation of false testimony by the state,” Contreras’s attorney Oscar Rene Flores said. 

The state said the immunity deal they gave Luna was necessary so she could testify without incriminating herself, and that that her testimony was not used to discredit her.

A new hearing date has yet to be set. 

READ ALSO: Mother of slain Donna High School student reacts to guilty verdict