Mark Whitten is a homicide detective with the Los Angeles Police Department's West Bureau. From 2000 to 2001 he worked in the Narcotics Bureau.
In 2012-2013, he and his partner investigated the murder of Gloria Dayton and arrested Andre La Cosse. In the trial he was called as a witness by both the prosecution and the defense. As a prosecution witness he testified as to the basic outlines of the case. Defense attorney Mickey Haller used his testimony to bolster the "alternate killer" scenario. Whitten testified that Dayton's cell phones were never found, so he had checked with the phone company to get a record of her calls. Under questioning by Haller, Whitten revealed that she had called the DEA's central number less than an hour after she was subpoened by Sylvester Fulgoni, Jr. in the case of Hector Arrande Moya. He further testified regarding the security video from the Beverly Wilshire Hotel. Whitten was a reluctant witness on these points because he knew they supported the idea that someone else had killed Dayton.