Mark McClish was a federal law enforcement officer for 26 years. He started his law enforcement career in 1983 with the U.S. Secret Service Uniformed Division. During the two years he was with the Secret Service he was assigned to the White House. His main duties were protecting the White House complex. He would also on occasion provide protection for President Reagan when the President traveled. In 1985, he was hired by the U.S. Marshals Service and served as a Deputy U.S. Marshal in Springfield, IL. This change allowed him to focus more on investigations and less on protection. He worked numerous federal fugitive cases and assisted local law enforcement in apprehending state fugitives. He also worked on a "Warrant Apprehension Narcotic's Team" which was a national drug task force.
In 1990, Mark was promoted to the position of Inspector/Instructor at the U.S. Marshals Service Training Academy located at the Federal Law Enforcement Training Center in Glynco, GA. He taught at the Training Academy for nine years serving as the lead instructor on interviewing techniques. He used this time to study deceptive statements and conduct research on deception. Based on his findings, he created the Statement Analysis techniques for detecting deception in a verbal and written statement. While assigned to the Training Academy Mark was also the lead defensive tactics instructor for the Marshals Service. Mark retired from the Marshals Service in 2009 and started Advanced Interviewing Concepts. His company provides interviewing skills training and assists investigators in analyzing statements.