DS Karen Williams was a police officer who investigated the murder of Tom King in December 2006. She investigated the fire at Tenant House in October 2007 which resulted in Andy Sugden being arrested and charged for Sarah Sugden's death back in November 2000. She investigated Rosemary King's disappearance in November and December 2007, and arrested Matthew King for murder. However, it was later revealed that Rosemary had been alive and took her own life on Christmas Day.
Williams investigated the charity money incident involving Freddie Yorke, Viv and Bob Hope between March and May 2008. Viv accidentally incriminated herself by admitting to moving funds, but claimed she put them back when she realised her mistake. DC Natalie Kemp didn't believe her and she was arrested. She investigated the death of Shane Doyle when his body was found in a lake by Daz Eden and Victoria Sugden in December 2008. She arrested Eli Dingle, but Eli revealed Debbie Dingle was behind it, and she was charged. Eli later changed his statement in February 2009, this time revealing Jasmine had murdered Shane. Williams was also present during Debbie's trial in March 2009.