Diane Nicholl grew up where guns were common. She has enjoyed shooting from the time she was ten years old and would go plinking with a .22 single shot rifle. She worked in the field of neurophysiology for 15 years before starting her own business, DTI Publications, Inc. where she teaches firearms courses and publishes firearms training books.

In the early 1990's, Diane started the Annie Oakley Society as a way to help women maintain and improve their shooting skills by providing monthly access to a range. She soon discovered that several female officers in her area were having trouble passing their weapons qualifications so she started offering private and group sessions for them.

Diane is a Colorado POST certified law enforcement firearms instructor and an NRA Training Counselor. She has done extensive research on the use of firearms in crime and self-defense. She is a member of the American Society of Law Enforcement Trainers, the International Association of Law Enforcement Firearms Instructors, the International Association of Women Police and the Colorado Law Enforcement Firearms Instructors Association.