Ashton Kutcher is expected to be called as a witness in the trial of a man accused of murdering his then-girlfriend in 2001.
There are reports that the star will testify against Michael Thomas Gargiulo, who has been charged with murdering 22-year-old Ashley Ellerin.
Ms Ellerin was attacked as she showered in her Los Angeles home and stabbed 47 times.
Prosecutors have called Gargiulo, who is accused of killing two other women, a "serial, psycho-sexual thrill killer who engages in the systematic slaughter of beautiful women".
The 37-year-old was arrested in 2008 after DNA evidence was recovered from the apartment of another victim, who survived an attack.
The Enquirer claims Kutcher will give evidence in court in the next few months.
The Two And A Half Men actor was dating Ms Ellerin at the time of her death and tried to ring her on the evening of 21 February when she was killed.
Kutcher, 36, has rarely spoken about the murder but has given written testimony to police.
It is understood he drove to Ms Ellerin's home when he could not reach her on the phone.
He reportedly looked through a window and saw what he thought was red wine pooled on the floor, but then left.
The woman's body was then found by her roommate.
Kutcher, who was married to Demi Moore between 2005 and 2013, started dating Black Swan star Mila Kunis in 2012. The couple have a daughter called Wyatt.
