The brother of disgraced former Honolulu prosecutor Katherine Kealoha, Rudolph Puana, who is accused of running an illicit prescription drug ring, pleaded guilty to a lone firearms charge Monday, one day before his criminal trial kicked off.

Puana, a Big Island anesthesiologist still facing more than 50 criminal counts related to health care fraud and prescribing thousands of opioid pills for illegitimate purposes, admitted in the U.S. District Court of Hawaii to possessing a gun while being addicted to drugs, a federal felony.

The charge carries a maximum penalty of 10 years in prison.

Federal prosecutors say Puana wrote unnecessary opioid prescriptions for several close friends, who would either sell the drugs or use them to barter for cocaine, to which Puana admitted he was addicted while owning a collection of guns.

Puana initially obtained the cocaine through a former employee at his pain management clinic who would place bags of the drug in a drawer in the procedure room in the facility, where Puana also kept a Glock semi-automatic pistol, according to court documents.

In 2018, Puana’s office manager began purchasing the cocaine, which cost $100 per bag, prosecutors said. Over a six-month period, Puana’s office manger, who is not named in court filings, bought Puana cocaine one to three times a month.

In August 2018, Puana admitted his addiction to his ex-wife and business partner, Lynn Welch, who arranged for him to travel to the Betty Ford Clinic in Minnesota for inpatient drug abuse treatment.

While at rehab, Puana called Welch and asked her to go to a drawer in a treatment room at the pain clinic to retrieve his gun, as well as some other personal items, which he wanted her to deliver to his current wife’s address in Waimea, prosecutors said.

Puana, who knew he was under investigation when he returned from rehab,  took his cache of guns — nine in all — to a Waimea hunting shop to “hastily sell them off,” according to court documents.

He successfully sold most of the weapons, which included handguns, rifles and a shotgun. Federal investigators have since seized the weapons as evidence in the case against Puana.

Sentencing for the gun charge will occur after the jury reaches a verdict on the remaining counts in Puana’s criminal trial, which is expected to take up to two weeks.

Jurors are expected to hear from Puana’s sister, former Honolulu deputy prosecutor Katherine Kealoha, who is currently serving a 13-year sentence at a federal prison in California on corruption charges involving Puana and Kealoha’s ex-Honolulu police chief husband, Louis Kealoha.

The jury is also set to hear from Puana’s close friends — Christopher McKinney, Josh DeRego and Elena Rodriguez — who prosecutors say received unnecessary prescriptions from Puana for thousands of oxycodone pills.

Puana’s defense team plans to argue that the prescriptions were for legitimate medical purposes, according to a trial brief Puana’s attorney Clinton Broden submitted earlier this month.