One of three California prison officers arrested in connection with the death of a mentally ill prison inmate has allegedly professed his innocence.

Rafael Rodriguez, 27, and two colleagues Matthew Farris, 27, Jereh Lubrin, 28, were arrested on September 3 after Michael James Tyree, 31, was found unresponsive in his cell on August 27.

Rodriguez alleged the uniform he wore on the night of the Tyree’s death was clean, the San Jose Mercury News reported.

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He refuted claims from one inmate who allegedly witnessed the guards entering Tyree’s cell.

“It sucks being in here for something I didn’t do,” he told the newspaper in an interview from jail.

The guards were arrested after medical examiner Dr Joseph O’Hara said the alleged victim died of multiple blunt force injuries, visceral lacerations and internal bleeding.

“[Tyree’s body] revealed multiple cutaneous blunt-force injuries such as contusions, abrasions and lacerations in addition to lacerations of the liver and spleen with significant collection of blood in the abdominal space,” Dr O’Hara said in an email, according to The New York Times.

Tyree was reportedly waiting for a bed at the Momentum Crisis Residential centre – a 24-hour residential treatment program – and was temporarily being held at Santa Clara Correctional.

About 50 people marched outside Santa Clara County Main Jail in San Jose, California, to demand better protections for inmates, Daily Mail reported.

The prison officers were held in custody without bail on suspicion of the murder.