Mr. Spear’s death in December 2012 was seen as highlighting the culture of violence and the code of silence among guards that has long existed at Rikers.

Image Brian Coll, a former Rikers Island guard who was convicted in the death of an inmate. Credit... New York City Department of Investigation

The United States attorney’s office in Manhattan, which has made violence at Rikers a focus of its civil rights investigations and prosecutions, said Mr. Coll should receive a “significant” sentence that “approaches” the 30 years recommended by the court’s probation department, and is “well beyond” the roughly four to six years Mr. Coll’s lawyers have recommended.

The jury found that Mr. Coll had deprived Mr. Spear of his constitutional right to be free from excessive force and that Mr. Coll’s actions had resulted in Mr. Spear’s death — for which he can face up to life in prison.

“Coll’s conduct was brutal; it was violent, it was willful, and it was callous,” the office of Joon H. Kim, the acting United States attorney, wrote.

Mr. Coll is to be sentenced on Wednesday by Judge Loretta A. Preska of Federal District Court.

Mr. Spear, 52, was a pretrial detainee in an infirmary unit at Rikers when Mr. Coll assaulted him after they got into a dispute in December 2012. At the time, prosecutors have said, Mr. Spear had heart disease, diabetes and end-stage renal disease that required dialysis. He also used a cane and wore a bracelet that said he was at “risk of fall.”