As with practically all factors that go into security clearance applications, a misdemeanor may or may not affect your security clearance application. The federal government takes any offense involving alcohol, drugs, firearms or sexual conduct very seriously and a related misdemeanor may disqualify you. The further in the past that the misdemeanor occurred, the less likely it is to affect your application, and if the misdemeanor occurred over 10 years ago, you may not even need to report it on your application.
Criminal conduct is one of the 13 areas that security personnel investigate when evaluating a security clearance application. Security personnel are charged with determining if a given applicant is a security risk, and they take past charges seriously; the website Security Clearance Jobs reports that past charges is one of the top four reasons that security personnel deny applications.
Security personnel and the adjudication guidelines weigh misdemeanors much less than felonies. If your misdemeanor occurred over seven years ago (10 years for a Top Secret clearance) you do not have to report it on the SF-86, the "Questionnaire for National Security Positions," that serves as a security clearance application.
Sex, Drugs and Alcohol
However, the SF-86 requires you to report any charge of any kind involving drugs, alcohol, firearms or explosives or sexual conduct. While the federal government takes any of these charges seriously, a misdemeanor in this area does not automatically disqualify you. Security personnel take it as a signal to investigate the circumstances and weigh the incident against recent behavior and demonstrated judgment (or lack thereof) in other situations. In most cases, you have an opportunity during an interview to explain the situation.
Reporting a misdemeanor does not automatically disqualify you from a security clearance. Hiding or misrepresenting information on your application not only disqualifies you but counts as a felony. Report all information truthfully and accurately and do not hide past actions, even if you think they may disqualify you.