Federal prosecutors are recommending a prison sentence between nine and 11 years for a man tied to the murder of a Chicago socialite in Bali.

Robert Bibbs, 26, pleaded guilty in December to conspiracy to commit the foreign murder of a U.S. national, telling U.S. District Judge Rebecca Pallmeyer that he knew Sheila von Wiese-Mack’s life was in danger when his cousin left for Indonesia in August 2014.

Sheila von Wiese-Mack

A suitcase containing von Wiese-Mack’s body was found in the trunk of a taxi outside the St. Regis Bali Resort later that month.

Authorities say Bibbs’ cousin, Tommy Schaefer, bludgeoned von Wiese-Mack to death after receiving text messages filled with encouragement and advice from Bibbs.

In the sentencing memorandum filed Monday, federal prosecutors argued Bibbs “certainly could have prevented the murder had he contacted law enforcement.”

Prosecutors also asked the court to consider his ongoing use of marijuana as a factor in his sentence, though he does not have any prior criminal convictions. Bibbs tested positive for cannabis 11 times despite the court’s directive that he stay away from illegal drugs.

Von Wiese-Mack’s daughter, Heather Mack, and Schaefer were convicted  in Indonesia. Schaefer, 23, was sentenced to 18 years in prison for beating von Wiese-Mack to death. Mack, 21, was sentenced to 10 years for helping.

Heather Mack, left, and her boyfriend Tommy Schaefer, right, both from Chicago, Ill., in a court room during they witness a trial in Bali, Indonesia, Wednesday, March 11, 2015. The couple is charged with murdering Mack’s mother, Sheila von Wiese-Mack, whose badly beaten body was found in a suitcase in the trunk of a taxi outside an upscale hotel in the resort island last year. | Firdia Lisnawati / AP

However, Mack recently acknowledged she was under threat of prosecution in the United States, citing an “ongoing federal criminal proceeding” in a court filing in February. A federal magistrate judge also signed off in January on a search of an iPhone FBI investigators believe belonged to Mack.

When Bibbs pleaded guilty, he described to the judge a “situation” in 2014 with Mack, who was pregnant but was being encouraged by her mother to “kill the kid,” who complained about the race of the father, Schaefer.

Bibbs said those actions drove Mack to want to get rid of her mother.

In fact, Schaefer told Bibbs that Mack had offered him $50,000 to kill her mother, prosecutors say. And when Mack visited Bibbs’ home in summer 2014, authorities said Mack told Bibbs she wished her mother was dead and asked him if he knew someone she could pay to do the job.

Meanwhile, Schaefer thought he could make up to $11 million off von Wiese-Mack’s murder, through Mack’s inheritance. Bibbs also thought he would get a cut. In the sentencing memorandum, prosecutors argue “although unwilling to kill von Wiese himself, [Bibbs] wanted to benefit from her death.”

The feds have said Mack and her mother arrived for a vacation in Bali on Aug. 4, 2014. Bibbs told the feds he knew Mack wanted to try to kill her mother there.

Authorities have said Schaefer arrived on the island Aug. 12. Mack allegedly told him in a text message they should wait until her mother “passes back out” before trying to kill her.

While waiting, Schaefer texted Bibbs and said an earlier attempt by Mack to kill her mother by overdose had failed. Bibbs suggested Schaefer try to drown her in the ocean or “go sit on her face wit a pillow then.” When Bibbs asked Schaefer by text, “What would u do?” Bibbs replied, “If it’s no cameras then,” followed by an emoji of a hand indicating “OK.”

Eventually, authorities say Schaefer texted Bibbs: “This is for you n—a. And the fam. One time. Here I go. Pray for me cuz.” Bibbs replied, “Done. It’s go time.”

After the murder, authorities say Bibbs told Schaefer by text that von Wiese-Mack “wasn’t a good person” and “there wasn’t any positive energy released from her body.”

Bibbs told the judge in December he wasn’t expecting Schaefer to actually go through with it. He told her, “I thought Heather was going to do it.”

“I never thought that my cousin would do anything like that,” Bibbs said.