A 44-year-old woman has been arrested on suspicion of the murder of 18-year-old Jonathan Cairns in Ballykelly 20 years ago.
The teenager was attacked as he made his way home from a night out in the early hours of 25 April 1999.
He was found buried in a shallow grave in Loughermore Forest.
A man was jailed in 2002 for helping to dispose of the body but no one has ever been charged with Mr Cairn's murder.
Police said on Tuesday that a 44-year-old woman has been arrested in the Dungiven area on suspicion of murder.
Detective Inspector Adrian Brown said: “I continue to appeal for information in relation to Jonathan’s murder. For over 20 years, Jonathan’s family and friends have suffered intolerable grief and they deserve answers.
“I understand their desire to see justice done and I believe that people within the Ballykelly community have information that could assist my investigation.
“Some people were not prepared to come forward at the time for a variety of reasons but I am asking people to search their conscience and think again. Circumstances and loyalties may have changed over years and it is never too late to do the right thing.
“Anyone with information should call detectives on 101. Or, if someone would prefer to provide information without giving their details, they can contact the independent charity Crimestoppers and speak to them anonymously on 0800 555 111.”