Detective Hudson is a minor character in Seinfeld. He is played by James Pickens Jr.
In "The Wig Master", although he didn't physically appear, his voice was heard when he arrested Cosmo Kramer because he thought Kramer was a pimp because of the outfit Kramer was wearing, having a cane, and fighting with a prostitute over money.
In "The Finale, Part 2", he comes to Latham District County Court to testify against Kramer. He told District Attorney Hoyt that he got a tip that a lot of prostitutes had been turning tricks in the parking lot and that's when he arrested Kramer.