The episode titled ‘A Hidden Clue’ of Investigation Discovery’s ‘On the Case With Paula Zahn’ and ABC’s ’20/20: What the Killer Left Behind’ chronicles the horrific killing of 20-year-old Amanda Plasse in Chicopee, Massachusetts. The tragedy left the entire community shaken to its core, while grief took over Amanda’s loved ones. Despite the detectives’ best efforts, they couldn’t crack the case until two years later, when a hidden clue in her bedroom led them to the perpetrator. The documentaries feature insightful and emotional interviews with the deceased woman’s loved ones and officials linked to the investigation.
Amanda Plasse Was Found Dead in Her Kitchen by Her Then-Boyfriend
Born on December 11, 1990, to Michelle Mathieson, Amanda Lynn Plasse was the middle child of three, with a sister named Aimee Lee Plasse and a brother. Described as creative, artistic, and free-spirited, Amanda was a social butterfly who made friends easily. With aspirations to enter the journalism industry, she moved out of her family home and relocated to a third-floor apartment in Chicopee, Massachusetts. In order to pay the bills, she began waitressing at the local Friendly’s restaurant. On the personal front, in August 2011, she began dating a guy named Seth Green.
With so many things to look forward to, Amanda’s life came to an abrupt halt as fate intervened. On the evening of August 26, 2011, Seth discovered Amanda’s remains in the kitchen of her apartment and immediately called 911. When the authorities arrived at the scene, they found the 20-year-old woman with more than a dozen stab wounds, out of which about seven were deemed fatal. Upon inspecting the crime scene, they noticed that a window had been broken from the inside. They also managed to collect a partial palm print off the shattered glass. Moreover, the detectives found a bloody shoeprint near the remains and an unknown DNA under her fingernails. The autopsy revealed that she was not sexually assaulted and had died of multiple stab wounds. Without wasting any time, a homicide investigation was launched.
Detectives Suspected Several of Amanda Plasse’s Acquaintances
As part of the investigation, the authorities interviewed Amanda Plasse’s neighbors in order to check if someone had noticed something strange on the day of the murder. One of the neighbors claimed to have seen Amanda collect her mail around 4 pm on the fateful evening, while another reportedly witnessed a white sedan speeding away from her house around 4:30 pm. Since her boyfriend, Seth Green, was the one who found her remains and called the police, the detectives brought him in for questioning. During the interview, he revealed that they had begun dating just a few days earlier. He told the officers that he was working late that evening and couldn’t give Amanda a ride to the restaurant, something he had been doing for a while.
When he stopped by the restaurant to meet her after 6 pm, he learned that she hadn’t come in yet. Concerned about her well-being, he drove to her house and discovered the crime scene. He also told them that he could not find his pocket knife. Despite his shaky alibi, the police cleared him as a suspect through DNA testing. However, he led the detectives to Amanda’s obsessive ex-boyfriend and co-worker, Jesse, who became a person of interest. He became all the more suspicious when the investigators learned that Jesse and Amanda had gotten into a heated argument at the restaurant the day before the murder. During his first interrogation, Jesse lied about being with his friend at the time of the killing.
When confronted about the same in the second interview, he admitted that he had been alone at the time, as he went to a liquor store after collecting his final check from the restaurant where he worked with Amanda. After verifying his account through cell phone records, the authorities eliminated him as a suspect, too. One of Amanda’s friends, Mercedes, was also considered a potential suspect until no evidence linked her to the crime scene. As the leads ran out, the case went cold for about two years until a clue in her bedroom photo cracked the case wide open. Upon zooming into Amanda’s whiteboard, they read a small note that read “Dennis Was Here,” dated August 8, 2011, a couple of weeks before the murder. That’s how they identified Dennis Rosa-Ramon as a suspect in the case.
The Killer Weaved Different Stories Throughout the Interrogation
At the time of the murder, Dennis Rosa-Ramon not only lived a couple of blocks away from Amanda but also had a rich criminal history. In order to question him regarding the case, the detectives tracked him down in a neighboring town. After running into him on the street outside his residence, they had a small conversation with him, during which he smoked a cigarette and claimed that he didn’t know any Amanda and had nothing to do with her murder. After he went on his way, the detectives collected the cigarette he had discarded so that they could test his DNA against the forensic evidence of the crime scene.
When Dennis realized the same, he came to the police station the following day and admitted that he had met Amanda on the street a few weeks prior to the murder. At first, he told them that he had never been inside her apartment, but later, he changed his story multiple times. Eventually, he said that he was in her house when Amanda was killed, but claimed that he was just a witness. However, his sneakers were found to be consistent with the bloody footprint found at the scene of the crime and his DNA was found under Amanda’s fingernails. Thus, in November 2013, Dennis Rosa-Ramon was arrested and charged with murder.
Dennis Rosa-Roman is Currently Incarcerated at a Massachusetts Prison Facility
Since Dennis Rosa-Roman decided to plead not guilty to the charges against him, his case went to trial, which got underway on June 23, 2016. During the trial, the prosecution presented a series of forensic evidence that linked him to Amanda Plasse’s murder. Thus, after days of testimony, the jury deliberated for five hours before reaching a verdict. Thus, in early July 2016, Dennis was found guilty of first-degree murder. Consequently, he was sentenced to life in prison without the possibility of parole. Nearly four years later, the killer filed a motion to get his conviction overturned, but his request was denied by the Court of Appeals.
In a shocking turn of events, in October 2025, Amanda’s mother, Michelle Penna, received a notification about the possibility of Dennis’ parole in 2028. It was the result of a 2024 Massachusetts Supreme Judicial Court decision that deemed mandatory life sentences without parole for “emerging adults” unconstitutional. Michelle opened up about her frustration during a conversation with Western Mass News, stating, “He was convicted but now, you’re telling me because he was 20 that he’s eligible for parole. You can enlist for the military at 17,18, you can register to vote, but because you committed a crime now, all of a sudden.” As of today, Dennis Rosa-Roman is serving his sentence at Souza Baranowski Correctional in Lancaster, Massachusetts, awaiting his parole eligibility date.
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