POCATELLO — Bannock County prosecutors are now saying two California teenagers conspired to murder an elderly Pocatello woman in March, according to amended criminal complaints presented during a Wednesday hearing at the Bannock County Courthouse.

The amended complaints charge Dustin Garrett Alfaro, 18, and Isaac Angel Rodriguez-Romero, 17, both of Marysville, California, each with one count of principal to murder in the first-degree and one count of conspiracy to commit murder in the first-degree for allegedly planning and carrying out the fatal stabbing of 87-year-old Pocatello resident Arlyne Koehler on March 19.

These new charges are replacing the previously filed felony first-degree murder charges Alfaro and Rodriguez-Romero were facing for allegedly murdering Mrs. Koehler.

The amended complaints mark the latest development in what could become a capital murder case if prosecutors elect to seek the death penalty against Alfaro. The amended criminal complaints provide details about several overt acts Alfaro and Rodriguez-Romero committed before murdering Mrs. Koehler, prosecutors said.

The amended criminal complaints state Alfaro and Rodriguez-Romero not only entered Pocatello via Interstate 15 and drove to a location near Mrs. Koehler’s home on McKinley Avenue, but the complaints also allege the California teenagers walked to the back of Mrs. Koehler’s home and entered her home through an unlocked window before allegedly killing her.

Moreover, the amended complaints state that Alfaro and Rodriguez-Romero “did willfully, unlawfully, deliberately, with malice aforethought and with premeditation … in the perpetration … of robbery or burglary, kill and murder Arlyne Koehler … by striking her repeatedly with a sharp object or knife.”

The amended complaints also include language stating that Alfaro could have aided or abetted Rodriguez-Romero, or vice versa, in the killing of Mrs. Koehler.

Though the attorneys representing Alfaro — Scott Andrew and Dave Martinez of the Bannock County Public Defender’s Office — as well as those for Rodriguez-Romero — Bradley Willis and Robert Otto Eldredge Jr., both of Pocatello — argued that the amended complaints were unfair to their clients considering their preliminary hearings are scheduled for next week, the judge handling both cases, Aaron N. Thompson, issued an order Wednesday approving the amended complaints.

Thompson will determine at next week’s preliminary hearings if there is enough evidence for prosecutors to take the accused teenagers’ cases to trial. Prosecutors said the amended complaints will definitely help prove the teens are guilty.

The principal to murder charge makes it so that prosecutors are no longer forced to present evidence that shows who actually carried out the fatal stabbing inside Mrs. Koehler’s home. With a principal to murder charge, the penalty remains the same as first-degree murder, but prosecutors only have to prove one teenager or the other actually committed the crime of murder and also provide evidence that connects the other teen to the crime.

And with the added conspiracy charge, both teenagers essentially face an additional count of murder in the first degree, except prosecutors only have to prove the teenagers conspired or planned to kill Mrs. Koehler, not that they actually committed the crime of murder.

Conspiracy is an agreement between two or more people to do something unlawful. To prove the crime of conspiracy, prosecutors must establish three elements: that an agreement to commit an unlawful act existed, that the defendants had knowledge of the agreement and voluntarily participated in it; and that an overt act was performed by at least one of the co-conspirators in furtherance of the conspiracy.

The principal to murder charge and conspiracy to commit murder charge each carry the same maximum penalty as first-degree murder, which is the death penalty in Alfaro’s case and up to life in prison for Rodriguez-Romero, who can’t legally face the death penalty because he was not age 18 or older when the alleged crime occurred.

Prosecutors have not yet commented on whether they will pursue the death penalty against Alfaro.

Prosecutors originally filed the amended complaints last week. However, there were errors in the complaints, according to Jonathan Radford, a deputy prosecutor with the Bannock County Prosecutor’s Office, and to correct the issues prosecutors withdrew and refiled the documents later in the week.

Thompson held Wednesday’s hearing to address the withdrawal of the incorrect complaint and to field arguments from prosecutors and Alfaro’s and Rodriguez-Romero’s attorneys on the corrected version.

Alfaro and Rodriguez-Romero are each currently incarcerated on $1 million bonds. Alfaro is being held at the Bannock County Jail and Rodriguez-Romero is being held at the 6th District Juvenile Detention Center, both in Pocatello.

Authorities have not yet commented on what caused them to believe Alfaro and Rodriguez-Romero allegedly murdered Mrs. Koehler, who lived alone. Family members found her dead inside her Pocatello home on March 19.

Many of the documents that could shed light on what may have happened inside Mrs. Koehler’s home, such as police reports and probable cause affidavits, remain under seal by judicial order.

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.

Alfaro’s preliminary hearing is scheduled for Sept. 3 and 4 and Rodriguez-Romero’s hearing is on Sept. 5 and 6.

Both preliminary hearings will be held at the Bannock County Courthouse.