Johnny Rider and Cassandra Bjorge
Johnny Rider (L) and Cassandra Bjorge (R) face murder charges in Georgia Gwinnett County Sheriff's Office

A Georgia girl and her boyfriend have been sentenced to life after they were convicted of killing the former's grandparents in April 2017. The duo had also thrown a drug-fuelled house party for their friends after committing the crime, leaving the bodies to decompose in another room.

17-year-old Cassandra Bjorge and her boyfriend Johnny Rider, 19, killed the girl's grandparents — Randall and Wendy Bjorge, both 63 — in their home in Lawrenceville. Court documents stated that Cassandra was living with them at the time of the attack and decided to kill the pensioners because she "basically had enough" of them.

While sentencing them, Judge Debra Turner said the case was one of the worst she has come across so far. "I'm not sure I've ever imagined such a well-planned, despicable, heinous act to be committed by two such young people. Your behaviour lacks any sense of humanity or morality," Turner told Rider and Cassandra after they entered their guilty pleas on Friday (2 February).

On the night of the attack, the couple had waited outside the house until the lights went out. They then entered the old couple's residence and beat them with a hammer and a baseball bat before slitting their throats.

Police said that Rider and Cassandra kept the bodies for over a week inside the house by sealing the room with caulk to hide the smell until they were eventually discovered on 8 April 2017.

While Cassandra remained silent during the sentence hearing, her boyfriend apologised for the crime. He said, "I would like to express my deepest apologies to the Bjorge family. I'm so sorry for the pain and grief I have caused all of you.

"I know what I have done is abominable and evil and is deserving of hellfire," the teenager added as reported by the Daily Mail.

The duo had pleaded guilty to charges of murder, aggravated assault and theft. They also faced armed robbery and aggravated battery charges, which were dismissed later, AJC.com reported.

Cassandra and Rider were each given two life sentences with the possibility of bail in 60 years, plus 21 years to be served concurrently with the life sentences.

Meanwhile, the family members of Randall and Wendy Bjorge are still in shock and "haunted" by what happened. Sylvia Bjorge Berman, the elderly couple's daughter, has experienced "persistent anxiety and a profound sadness" since her parents' deaths, according to media reports.

While, their son, Chris Bjorge was quoted as saying by WSBTV that he is "still in shock and disbelief that such an event has occurred". "I have anxiety that I can barely describe and anger that is boiling deep."