An award-winning member of the police force, Officer David Marks prepared for his career by studying criminal justice at Highline Community College and Kaplan College. Officer David Marks went on to attend the Basic Law Enforcement Academy and Washington State CORE Academy through the Criminal Justice Training Commission from 2004 to 2006. During this period, he also served as a correctional officer for the Washington State Department of Corrections. His responsibilities included supervising inmates in the McNeil Island correctional facility, responding to emergencies, inspecting facilities to ensure they met state government standards, and aiding in the counseling and rehabilitation of offenders.

From 2006 to 2018, Officer Marks held multiple positions within the police department of the city of Langley, Washington. From 2006 to 2013, he served as a police officer, and received the Mayor's Excellence Award for "excellence in police department leadership," as well as for "solving a commercial burglary." As a result of his achievements, he advanced to the position of chief of police from 2013 to 2018, during which time he implemented a variety of successful initiatives. He furnished patrol cars with automated external defibrillators (AEDs) and patrol officers with the opioid-blocking medication Naloxone. Additionally, he assisted government officials in budget planning by completing a study of the police department, and increased the training programs for the department’s staff.