Derek Mahlum was born and raised in Wolf Point, Montana. He started his career with the Wolf Point Police Department in 2004. During this time he worked with various state, local, tribal and federal agencies policing Indian Country.
In 2005, he took a position with the Havre Police Department where he worked until 2011. During this time, he served as a firearms instructor, field training officer and left the agency as a patrol sergeant. During this time, he enjoyed seeking out the most difficult of cases in order to develop them to be presented to the appropriate state or federal attorney for prosecution.
In 2011, he took a position with the Great Falls Police Department. He was later assigned as a general case detective in 2015 where he is currently assigned to the Investigative Services Unit. During his time, Det. Mahlum has led and assisted with numerous homicide/death investigations. This position allows him to investigate numerous violent crimes to include robberies, suspicious deaths, shootings and major assaults. Det. Mahlum is also pursuing certification as a Crime Scene Analyst with the International Association of Identification.