BILLINGS, Mont. (AP) – Attorneys for a Wyoming teenager charged in a double slaying on Montana’s Crow Indian Reservation are fighting attempts by federal prosecutors to have the suspect examined to see if he’s competent to stand trial.

Jesus Deniz Mendoza could face the death sentence if convicted in the shooting of a couple who stopped to help him along a roadway near Pryor.

His attorneys say Mendoza, 18, has a significant mental illness. But there has been no indication he’s incompetent to understand the charges against him and assist in his own defense.

However, the attorneys did not rule out a future exam in a Monday court filing. Rather, they suggested to U.S. District Judge Susan Watters that it was their role to arrange and oversee such an evaluation, not the prosecution’s.

“Mr. Mendoza’s defense team takes their role in the assessment of this issue very seriously and, when and if the time is ever ripe for raising this issue, will do so,” defense attorneys David Merchant and Donald Knight wrote.

Assistant U.S. Attorney Lori Harper Suek filed a sealed request on Feb. 8 seeking a court-ordered competency exam for Mendoza.

The request was revealed in the court documents filed Monday.

Mendoza is accused of fatally shooting Jason and Tana Shane and wounding their daughter on July 29 after the family stopped to help Mendoza. He has pleaded not guilty to 12 charges, including two counts of first-degree murder, carjacking, attempted murder and multiple assault and firearms charges.

Prosecutors have until July 1 to say whether they intend to seek Mendoza’s death if he’s convicted.

The case is in federal court because the U.S. Justice Department has jurisdiction over major crimes in Indian country.

Watters set a tentative Sept. 6 trial date. That date would be cancelled and likely pushed back if the U.S. Attorney’s Office pursues a death sentence.

Mendoza faces a separate accusation of attempted second-degree murder in Washakie County, Wyoming, where authorities say he shot a man at a campground near the small town of Ten Sleep during a 2013 robbery attempt.