"They beat a confession out of me, 14 hours," Caldwell told Newsday as he was led from a police precinct Sunday.
Steven Browne, 29, of Mastic Beach, pleaded not guilty to hindering prosecution.
Koch, 44, of Mastic Beach, was reported missing by his girlfriend on Dec. 20. His body was found four days later in the trunk of a sedan parked at his company's lot, police said. He had been shot twice in the torso.
Suffolk County Police Det. Sgt. Thomas Groneman said Caldwell, who worked at the towing company and lived in a trailer on Koch's property, shot Koch in an argument over "personal issues."
Browne, who had been a friend of both men, helped Caldwell put Koch's body in the trunk and destroy evidence, Groneman said.
Caldwell was held without bail and Browne was in custody on $500,000 bail Sunday.