Many eligibility criteria normally apply, which may be related to age, nationality, height and weight (body mass index), medical history, psychiatric history, illicit drug use, criminal record, academic results, proof of identity, satisfactory references, and whether any tattoos are visible. A minimum standard of academic attainment may be required for entry, for certain technical roles, or for entry to train for a leadership position as a commissioned officer. Candidates who meet the criteria will normally also undergo aptitude test, medical examination, psychological interview, job interview and fitness assessment.