The boyfriend of actor Morgan Freeman's step-granddaughter has pleaded not guilty to second-degree murder over her stabbing death as newly-released documents showed he ranted about Christ and the devil to police officers after his arrest.

"I don't even know why I'm here right now," Lamar Davenport told two officers at a Manhattan precinct station house shortly after he was arrested on August 16 while standing over Edena Hines' body, a knife still sticking out of her chest, according to prosecutors.

Twenty minutes later, while being driven to a hospital, 30-year-old Davenport called Jesus Christ "saviour" and the devil "evil" before telling the officers to "repent for your sins", court papers showed. He also asked the officers if they believed in Jesus and complained his handcuffs were too tight.

"Beloved to her family and friends, Edena Hines had recently returned to New York City to pursue her acting career, but her life was tragically cut short before she could achieve her dreams," Manhattan District Attorney Cyrus Vance said.

A lawyer representing Davenport did not immediately respond to a message seeking comment. She told a judge her client was due to undergo a psychiatric evaluation tomorrow, the Daily News said.

Ms Hines, 33, is the step-granddaughter of Oscar-winning Freeman, who has said through a publicist that he thought of her as a granddaughter.

She was discovered on a street with at least 15 stab wounds to her chest and body.

After he was arrested Davenport was taken to a hospital where he was given sedatives, according to the court documents. He then awoke screaming: "Why did this happen? No, no! Why God?" the court papers said.