Colorado Jury Convicts Man Who Strangled Girlfriend to Death on Amtrak Train as She Tried to Escape Abusive Relationship
DENVER, COLORADO — A Colorado jury has convicted a man who prosecutors say strangled his girlfriend to death aboard an Amtrak train while their children slept nearby, ending a years-long effort to evade justice after the killing went unsolved for nearly seven years.
Murder Aboard Cross-Country Train
Angelo Valentino Mantych, 43, was found guilty Friday of first-degree murder in the 2016 death of 28-year-old Marina Placensia, according to the Denver District Attorney’s Office.
Placensia was pronounced dead after the train arrived at Denver Union Station following a trip from Wisconsin to Colorado. At the time, the couple and their four children were in the process of relocating from Racine, Wisconsin, to Denver.
Initial Investigation Raised Questions but No Charges
When emergency responders arrived, Placensia was unresponsive, and resuscitation efforts failed. Early autopsy results could not determine a definitive cause or manner of death, delaying criminal charges for years.
Investigators noted Mantych appeared emotionally distressed at the scene.
“Mantych appeared to be upset, crying, and vomited several times,” documents stated.
Mantych told authorities he believed Placensia was simply a heavy sleeper and said he tried repeatedly to wake her before realizing something was wrong.
At the time, no witnesses reported seeing an assault aboard the train.
Prosecutors Say Victim Was Trying to Leave
Years later, investigators uncovered evidence that Placensia had been planning to leave Mantych once they arrived in Denver, where family members were waiting to help her escape the relationship.
Assistant District Attorney Lara Mullin told jurors:
“He knows what is waiting at that train station is a collection of family members who are going to make sure he doesn’t go home with Marina and the boys,”
“Because things were at a breaking point.”
Prosecutors argued Mantych killed Placensia during the night, choking her in her seat while their children slept and other passengers remained unaware.
History of Severe Domestic Abuse Revealed
As the case was reopened, witnesses came forward describing years of violent abuse inflicted by Mantych on Placensia and her children.
Neighbors told investigators Mantych regularly beat Placensia, sometimes daily, and assaulted her shortly before the move.
Court records detailed allegations that Mantych:
- Slapped and punched Placensia during the move
- Grabbed her neck and pulled her hair
- Verbally degraded her while forcing her to move furniture
- Threatened children and physically abused them
One witness recalled hearing a child beg:
“Please stop, it hurts,”
To which Mantych allegedly responded:
“Get up, you little bastard.”
Placensia reportedly wore sweaters and sunglasses in the summer to hide injuries.
Autopsy Findings Later Confirm Homicide
Although early medical examinations were inconclusive, a follow-up forensic review in 2024 reached a definitive conclusion.
A forensic doctor determined Placensia died from suffocation, with injuries consistent with pressure applied to her face and obstruction of her nose and mouth.
“Ms. Placensia exhibits multiple areas of oral and perioral trauma consistent with asphyxia from suffocation,” the doctor wrote.
“The manner of death is homicide.”
Jury Delivers Guilty Verdict
After approximately five hours of deliberation, the jury returned a guilty verdict on Friday.
Mantych is scheduled to be sentenced on January 9, where he faces the possibility of life in prison.
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