5 key details about William Dennis' case ahead of Snapped

Snapped season 26, episode 9, which initially aired on October 27, 2019, follows William Dennis' case. On Halloween night in 1984, William Dennis walked up to his ex-wife's home in San Jose, California, in a masked costume.

His ex-wife, Doreen Erbert, who was married at that time to Charles Erbert and also had a daughter with him, opened her front door, expecting trick-or-treaters. But she was met by a masked killer, wielding a machete. Doreen was also eight months pregnant at that time.

Dressed in a wolf mask, Dennis hacked her to death, decapitating her, and tearing open her womb, causing her unborn son to fall out and die. Doreen too succumbed to her injuries, leaving her four-year-old daughter traumatised and her husband Charles with grief.

What unfolded that night was not random violence but the culmination of years of grief, bitterness, and obsession rooted in the tragic drowning of Dennis’s young son, whom she shared with William. The episode re-airs on Oxygen tonight.

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William Dennis' crime: 5 details explored

William Dennis killed Doreen Erbert (Image via Getty)

1. The Halloween night attack

On October 31, 1984, the quiet San Jose neighborhood where Doreen Erbert lived with her husband Charles and daughter Deanna was shattered when a masked man knocked at her door. At the time, Charles had gone out to run an errand, leaving Doreen at home with their four-year-old daughter, Deanna. That evening, a man in a wolf mask and coveralls knocked at the couple's door, and Doreen thought it might be a trick-or-treater.

According to Oxygen, the masked man attacked her with a machete. He hacked Doreen, severing her hand, cutting through her skull, and slashing her abdomen. Doreen was eight months pregnant at the time. Her womb was torn open, and her unborn son was expelled and fatally injured. Deanna, who managed to hide behind the couch, survived the incident.

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2. Suspect identified

Charles returned minutes later to find his wife almost dead, and his unborn son lying nearby, dead. When authorities arrived at the scene of the crime, they noted slash marks on the front door and ceiling, which showed that a heavy-bladed weapon had been swung repeatedly.

According to Find Law, witnesses also reported seeing a man in a wolf mask loitering near the Erbert home earlier that evening and later walking toward a pedestrian overpass. This trail of sightings, combined with the evidence left behind, quickly pointed towards a man from Doreen’s past as the main suspect. It was her ex-husband, William Michael Dennis.

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3. The evidence from the crime pointed to Dennis

In the early hours of November 1, 1984, police arrived at William Dennis’s home. When Dennis answered the door, they noticed deep cuts on his hand, which he claimed came from carving a pumpkin. Inside his home, police found bloodstained clothing, bloody bandages, and a receipt label for a Stanley machete identical to the kind believed to be used in the killing.

Doreen was found hacked to death (Image via Getty)

Blood was also discovered on his truck and in his garage, and a trail of blood drops led from the Erbert home directly to his property, as per Oxygen. Moreover, officers even discovered that the wolf mask found at the crime scene matched one Dennis had worn the previous Halloween. They also found two handmade coffins and body bags in his shed, which suggested that he had long thought about killing Doreen and Charles.

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4. A motive identified

William Dennis and Doreen Erbert had a past full of unresolved grief and bitterness. They used to be married and even had a son named Paul. In 1980, Paul drowned in the backyard pool of the Erbert home. Although it was considered to be an accident, Dennis came to believe that Doreen was responsible, claiming that she even wanted him to die.

In 1982, Dennis sued Doreen and Charles for wrongful death, but the jury sided with them, according to Find Law. This made William Dennis feel that Doreen had gotten away, and he fixated on punishing Doreen himself. Witnesses testified that he remained consumed with anger for years, and even psychiatrists concluded that Paul’s death and the failed lawsuit triggered his mental health issues.

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5. Trial, conviction, and aftermath

At his trial, William Dennis’s defense claimed he was insane at the time of the attack, arguing that his delusions about Paul’s death had driven him into a psychotic state. Psychiatrist testimony described him as suffering from depression and dependent personality disorder, overwhelmed by grief. Dennis himself admitted to killing Doreen but claimed he hadn’t known she was pregnant.

However, the prosecution countered that his disguise, weapon, and the elaborate preparation for the murder indicated otherwise. According to Oxygen, the jury rejected his insanity plea, convicting him of first-degree murder for Doreen’s death and second-degree murder for killing the fetus. William Dennis was sentenced to death, but when California’s death penalty was overturned, his sentence was commuted to life in prison.

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Catch all about William Dennis' case on Snapped today.