After a decade-long pursuit of justice, a man has been convicted of first-degree murder for the death of his girlfriend on an Amtrak train. Angelo Valentino Mantych, 43, faced a jury on Friday, who took roughly five hours to reach a unanimous guilty verdict for the murder of 28-year-old Marina Placensia, as reported by Denver 7.

CrimeOnline previously detailed that Mantych was taken into custody in 2023, accused of committing the crime in 2016. The case had remained unsolved for years until new evidence led to charges being filed against him.

In the summer of 2016, Mantych, Placensia, and her four young children—three fathered by Mantych—embarked on a journey from Racine, Wisconsin, to Denver aboard an Amtrak train. Tragically, upon the train’s arrival at Denver’s Union Station on September 1, Placensia was found deceased.

According to a police affidavit, Mantych was seen on the station platform appearing visibly distressed, crying, and vomiting multiple times, raising immediate concerns and initiating a long investigation into the circumstances of Placensia’s death.

Mantych Placensia, and her four young children—three of them with Mantych as the father—boarded an Amtrak train in Racine, Wisconsin, on August 30, 2016, to travel to Denver. When the train arrived at Denver’s Union Station on September 1, Placensia was dead.

Mantych was reported to be on the station platform, an affidavit says, and he “appeared to be upset, crying, and vomited several times.”

Mantych told police the family had been in the process of moving to Denver. He said that about 20 minutes from their destination, he tried to awaken Placensia, but she didn’t respond.

The affidavit, however, stated that police at the scene saw bruises on Placensia’s body that “appeared to be consistent with an assault or struggle.”

Mantych reportedly attributed the bruises to Placensia being “banged up while moving.”

On the same day Placensia was found dead, her brother contacted police and told them that Mantych was abusive and should be considered a suspect in her death.

A week later, family acquaintances in Wisconsin told investigators that Mantych beat his girlfriend the day before they boarded the train. Witnesses said the couple often fought and that Mantych had been physically and mentally abusive.

One witness said Mantych beat her daily, and another said she had been hospitalized multiple times from his attacks.

Some of the witnesses said they suspected Mantych was abusing the children as well.

According to the affidavit, a friend of Placensia told detectives she heard Mantych threaten her, stating, “he would kill her if she left with the children.”

The autopsy report found 35 internal and external injuries on Placensia’s body.

Almost seven years later, in May 2023, Dr. Bill Smock, a nationally-recognized expert in asphyxia and suffocation, said he believed Placensia’s death was a result of asphyxia from suffocation. He declared her death to be a homicide, which the original medical examiner had not done.

“Suffocation was the cause of Ms. Placensia’s homicidal death and occurred from the application of pressure to her face and obstruction of the nose and mouth, and it created a hypoxic condition, which led to her death,” that report says. ” … The manner of death is homicide.”

Placensia’s father spoke with Denver 7 outside the courtroom after the verdict, and described the way he felt about the conviction as a bunch of special days, Christmas, New Year’s Eve, and his birthday, rolled into one day.

Mantych’s conviction carries a mandatory sentence of life in prison without the possibility of parole.

Sentencing is scheduled for January 9. The family and friends of the victim will be allowed the opportunity to speak out on the tragic loss of their loved one.

[Feature Photo: Angelo Mantych and Marina Placensia/Denver District Attorney’s Office]