POCATELLO — A teenager who may face the death penalty for allegedly killing a Pocatello grandmother in March was charged with another felony for a Saturday incident at the Bannock County Jail.

While incarcerated at the Bannock County Jail in Pocatello on charges of felony first-degree murder, conspiracy to commit first-degree murder and a felony enhancement for using a weapon during the commission of a felony crime, Dustin Garrett Alfaro, 18, of Marysville, California, allegedly destroyed the sprinkler system inside his maximum-security cell, resulting in an additional felony charge of malicious injury to jail property, according to court records.

Though he could face the death penalty for allegedly stabbing 87-year-old Arlyne Koehler to death while she slept in her McKinley Avenue home in Pocatello in March, the new felony charge carries a maximum penalty of five years in prison and up to $10,000 in fines.

Bannock County Prosecutors have not yet decided whether or not they intend to seek the death penalty against Alfaro.

Saturday’s incident began to unfold around 9:20 p.m. when Alfaro, using the jail’s intercom system, told a jailer he was “going to pop the sprinkler head,” in his cell, according to a Bannock County Sheriff’s Office report.

The jailer advised Alfaro it would not be in his best interest to damage or destroy any jail property as it would result in additional charges against him, the sheriff’s office said.

Alfaro allegedly told the jailer that it didn’t matter whether he was charged with another felony or not, and again, said he was going to break the sprinkler head, the sheriff’s office said.

A few minutes later, Alfaro allegedly used the intercom system to inform the jailer that he had broken the sprinkler head inside his cell into small metal pieces and that a jailer could come and pick up the pieces from him if they wanted, the sheriff’s office said.

The damage to the sprinkler head did not cause any flooding to Alfaro’s cell, the sheriff’s office said.

The jailer entered Alfaro’s cell and confirmed the sprinkler head was broken and advised Alfaro he would face additional criminal charges, which were filed Monday.

Bannock County Sheriff Lorin Nielsen said this was at least the third occurrence in which an inmate has damaged jail property this year. Last July, Nielsen said a riot broke out inside the jail involving up to 27 inmates, which forced the sheriff to reroute all incoming county 911 calls to other agencies so that every deputy under his command could respond to the detention center.

Nielsen said tensions among inmates because of severe overcrowding inside the jail caused the riot last year, but overcrowding was not an issue that prefaced Alfaro’s recent alleged destruction.

“We have had two or three of these destruction of jail property incidents this year,” Nielsen said. “It’s just a matter of control, defiance or a cry for attention. Jail is boring and restrictive and when these incidents occur, it’s typically because an inmate is trying to challenge the authority of jail staff.”

Already incarcerated with a $1 million bond, Alfaro also received a bond amount of $10,000 for the recent malicious injury to jail property charge.

A hearing to determine if there is enough evidence to take Alfaro’s malicious injury to jail property charge to trial has been set for Nov. 4 in front of 6th District Judge Scott Axline at the Bannock County Courthouse. Alfaro is also scheduled to appear at the courthouse in front of Judge Robert Naftz on Nov. 21 for a status conference regarding his first-degree murder charges.

Alfaro and another Marysville teenager, Isaac Angel Rodriguez-Romero, 17, allegedly murdered Mrs. Koehler in March, stabbing the woman over 55 times, the forensic pathologist who conducted her autopsy said at Alfaro’s preliminary hearing in September.

A son-in-law found Mrs. Koehler, who lived alone, dead inside her Pocatello home on March 19. The teenagers allegedly forced entrance into Mr. Koehler’s home through a back window before attacking the elderly woman while she slept, prosecutors argued during the September preliminary hearing.

Prosecutors presented evidence during the preliminary hearing last month that indicated the teenagers first targeted Mrs. Koehler for a home invasion and robbery before allegedly killing her.

Both teens were arrested on March 20 in California, less than 48 hours after Pocatello police held a press conference alerting the public about Mrs. Koehler’s murder.

The teens were extradited to Idaho to face charges for allegedly murdering Mrs. Koehler after authorities arrested them in California.

Because he is under age 18, Rodriguez-Romero is being held in the 6th District Juvenile Detention Center in Pocatello, also with a $1 million bond.

Rodriguez-Romero is scheduled to appear at the Bannock County Courthouse in front of Naftz on Dec. 5 for a status conference regarding his first-degree murder charges.

Because Rodriguez-Romero was a juvenile at the time of the murder, U.S. Supreme Court case law says it is unconstitutional for him to face the death penalty. He still faces a maximum punishment of life in prison if convicted.