By the time the Amtrak train rolled into Denver early on a September morning nine years ago, 28-year-old Marina Placensia was dead in car 510, seat 22.
Her boyfriend, Angelo Mantych, frantically alerted train staff that she was unresponsive just after the train pulled into Union Station at 7:12 a.m. on Sept. 1, 2016. The train’s assistant conductor, Joseph Benjamin, found Placensia slumped over in her seat, her bra above her breasts, not breathing. She was warm to the touch, and she wasn’t stiff.
But when Benjamin performed CPR, Placensia’s breath carried the unmistakable stale stench of death, he testified Tuesday at the start of the jury trial for Mantych, who was charged with his girlfriend’s murder seven years after her death.
The Denver Office of the Medical Examiner could not determine Placensia’s cause of death — she had 35 separate injuries to her body, including cuts and bruises, which witnesses and family members attributed to longstanding physical abuse from Mantych, now 43. None were serious enough to cause her death. She had advanced liver disease from alcohol abuse, but the medical examiner couldn’t point to that as her cause of death either.
The case went cold until 2023, when the lead detective left the Denver Police Department and joined the Denver District Attorney’s Office. He revived the investigation and sent Placensia’s case to Bill Smock, a physician with the Louisville Metro Police Department in Kentucky, who testified as an expert in the George Floyd case, for a second look.
Smock concluded she was smothered to death.
Prosecutors believe Mantych silently asphyxiated his partner at some point during the night in the dark train car. Defense attorneys argued she died of natural causes. None of the passengers or staff in the train car that night saw a confrontation between the couple, public defender Srinija Pernankil said during opening statements Tuesday.
“Not a single witness… heard fighting, arguing, struggling,” she told jurors in Denver District Court. “You will not hear from a single witness who saw or heard a conflict.”
Even Placensia’s four children, who were with the couple on the train, did not report a confrontation that night, Pernankil said. The prosecution’s expert witness, she said, came into the case years after the autopsy, looked at some photos and told prosecutors what they wanted to hear.
But Assistant District Attorney Lara Mullin said Smock saw what Denver’s autopsy missed: telltale signs of smothering. Investigators sent Smock photos of Palencia’s autopsy, the autopsy report, witness statements and scene photographs.
“What he saw immediately stood out,” Mullin said. “Injuries to the oral and perioral area of her mouth. Hemorrhaging inside her lips. Bruising on her jawline and face. What did these injuries say to Dr. Smock? It suggested this: smothering.”
Smock is expected to testify during the jury trial.
Denver investigators documented years of domestic violence between Mantych and Placensia ahead of the fatal train trip in a 12-page affidavit. Witnesses described Mantych beating Placensia, slapping her, giving her black eyes. They remembered that she wore long sleeves even in warm weather to cover up the injuries.
Placensia was planning to leave him once she arrived in Denver, one family member said, according to the affidavit. But Mantych had threatened to kill her if she ever tried.
Pernankil said her client was “not a perfect father, not a perfect husband,” but that his past domestic violence should not lead jurors to assume he killed Placensia on the train. Placensia suffered from severe liver disease and heart conditions that, coupled with her history of alcohol abuse, could have caused her death, Pernankil argued during opening statements.
Mantych told officers he tried to wake his girlfriend about 20 minutes before they arrived in Denver, and assumed she was sleeping deeply when she did not stir. He said he tried again 10 minutes before arrival and then sought help when she still did not respond, according to an affidavit.
Pernankil accused authorities of pursuing the case against Mantych in large part because Placensia’s family continually advocated for his arrest.
“They convinced themselves he must be the cause of Ms. Placensia’s death,” she told jurors. “…In the search for answers and the search for closure, the truth and the law should not be forgotten.”
The trial is scheduled to last through Dec. 15.
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