After he was convicted in August of several charges related to the torture and death of his then-girlfriend’s disabled son, Matt Christenson learned his fate Friday at his sentencing hearing.

Christenson, a 45-year-old from Auburn, Washington, was charged with brutally beating and abusing Otto Smith in 2014, ultimately causing his death in April of that year at the age of 18.

Prosecutors said he abused the severely autistic teen in various humiliating and painful ways, including binding his arms and legs, gagging him, wrapping his head in duct tape, and forcing him to take ice baths.

A jury heard details of the the alleged abuse of Smith and his younger brother and convicted Christenson of homicide by abuse, felony harassment, unlawful imprisonment and three counts of second-degree domestic violence. A judge agreed with prosecutors’ suggestion, giving him a 65-year sentence.

The punishment is about twice the typical sentence for a conviction such as his, due to the circumstances of his crimes.

According to authorities, the abuse began in January 2014, shortly after Christenson met Smith’s mother online. As he pursued the new relationship, prosecutors say he began systematically torturing her two teenage sons.

He reportedly moved in with the family, along with his 20-year-old son.

Among the details that led to Christenson’s conviction was the allegation that he forced Smith to wear garbage bags instead of pants, prevented him from eating and threw cayenne pepper into his eyes.

At one point, prosecutors say he shocked the teenager with a stun gun.

Smith reportedly died a short time after after a particularly brutal attack discovered by his mother.

After subjecting Smith to an ice bath, jurors heard that the defendant bound and gagged him and stuffed him under a chair in the living room. Christenson was reportedly sitting on another chair, smoking marijuana and drinking beer, when Backman found Smith and began trying to revive him.

According to the charges filed against Christenson, he and Backman transported Smith to a local hospital. Backman reportedly told hospital staff her son had fallen down a flight of stairs. After several days in the hospital and a longer stay at a rehabilitation facility, Smith died two days after he returned to his home.

Smith’s younger brother, who was 14 when the abuse began, was also reportedly subjected to much of the same treatment.

In December 2014, months after Smith died, Backman showed up at a hospital, where she initially identified herself as the victim of a kidnapping. Her story soon changed when she told a social worker that Christenson was an abusive boyfriend who was responsible for her son’s death.

The following November, she pleaded guilty to rendering criminal assistance in the first and second degree and was ordered into treatment for mental health and drug abuse. As part of her court order, she is also prohibited from contacting her surviving son.

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