OKLAHOMA - Jury selection began Monday in the case known as the 'Cathouse murders.'
It involved one victim who was a prostitute on a popular reality TV show.
Security is tight for the trial.
An extra security checkpoint was added in front of the courtroom after several death threats were made against one of the men on trial.
Denny Phillips and Russell Hogshooter face the death penalty in the murders of a drug dealer and three women.
Prosecutors said Denny is a leader in the Indian Brotherhood Gang, so it's not just every day security at the courthouse.
"It is rare. It’s in cases where there’s a risk to the defendant like, in this case, he’s a gang member, maybe even the shot caller of a prison gang, and there’s been threats on his life. There’s also concerns someone might try to break him out," said legal analyst David McKenzie.
The brutal murders happened in 2009.
Prosecutors said Denny led the plan to rob and kill known drug dealer Casey Barrientos.
Hogshooter is accused of helping in the murders.
Prosecutors said three women were killed to eliminate them as witnesses: Milagros Berrera, Jennifer Ermy and Brooke Phillips.
Brooke was a prostitute on the HBO series 'Cathouse.'
Brooke and Barrera were both pregnant.
"Credibility of witnesses is going to be crucial to this case. The government is going to put on witnesses that have been given deals, whose reliability is questionable," McKenzie said.
Also, a lot of time has passed.
One of the state's witnesses is David Tyner, who's serving life in prison without the possibility of parole.
In a deal with prosecutors, he avoided the death penalty in exchange for his testimony.
Tyner admitted to police he killed Barrientos and two of the women at the direction of Denny.
Hogshooter is accused of killing Brooke and setting all of their bodies on fire.
Denny and Hogshooter are both charged with conspiracy and six counts of murder.
Jury selection continues Tuesday morning.
The trial is expected to last 4-6 weeks.