The Pennsylvania police officer who received a tip about Luigi Mangione being spotted at a local McDonald's has said he and his supervisor were so sceptical that it was the suspected shooter they exchanged jokes about it.

Joseph Detwiler told a Manhattan courtroom on Tuesday that tip ultimately led to Mangione's arrest for the shooting of UnitedHealthcare CEO Brian Wilson in New York last December.

Mr Mangione, 27, who has pleaded not guilty to state and federal murder charges, was in court for a second day of proceedings to decide if evidence from his arrest is admissible in trial.

His defence team wants key evidence thrown out, arguing that he was not immediately informed of his rights.

"He said, 'if you get the New York City shooter, I'll buy you a hoagie from a local restaurant,'" Mr Detwiler said in court of text messages exchanged with his lieutenant. "I said: 'Consider it done.'"