This week, Laura looks at how a 30-year-old cold case was solved thanks to some impressive detective work, a few exciting advances in DNA technology, and… a piece of chewing gum.

Murder They Wrote with Laura Whitmore and Iain Stirling is available weekly on BBC Sounds. Subscribe now so you never miss an episode. Email us at [email protected].

Details of help and support with addiction are available at bbc.co.uk/actionline.