Stepanyan is the third person to be taken into custody since Voskanian was shot and killed Feb. 25 outside her Burbank home’s front door.
Two men — Arpiar Terrgalstanyan, 20, of Glendale and Armen Mangasaryan, 29, of Burbank — were arrested the same week of Voskanian’s death. The pair pleaded not guilty Feb. 27 to killing Voskanian.
All three are being held without bail, Robison said.
Police allege that Stepanyan planned the murder, Mangasaryan shot Voskanian, and that Terrgalstanyan was present at the killing.
The trio knew Voskanian because of an unpaid monetary debt, police said.
Voskanian answered her home’s front door at 12:20 a.m. Feb. 25 in the 4200 block of Jacaranda Avenue after she heard either a doorbell or knock and was shot once, officials said.
Her boyfriend, who also was inside the home during the shooting, found her lying on the ground near the front door.
Voskanian’s boyfriend called police, who then notified paramedics, but they were unable to resuscitate her, and she was pronounced dead at the home. Coroner’s officials said she died of a gunshot wound to her head.
Neighbors told police the couple were renting the home and moved into it about six months ago. Police recovered a handgun and seized a black Mercedes-Benz, which may have been used as a getaway car after the shooting.
If convicted, the trio could face the death penalty or life in prison without the possibility of parole.