Chris is Josh’s best mate. He was at the party but says he did not hit Josh. He wants to do all he can to help the police find Josh’s killer.
Chris offers to give a DNA sample as he wants to be ruled out of police inquiries. (See When and how police can take DNA samples).
Chris wants to be sure, though, that once his DNA is taken, the DNA sample and DNA profile will be destroyed as soon as he is cleared of suspicion. (See what the law says about keeping DNA samples and profiles).