Douglas P. Bernabei began his law enforcement career in 1977 with the Spring Valley Police Department has a part-time dispatcher while attending college first at Illinois Valley Community College and then Illinois State University. In 1982, he graduated from Illinois State with a Bachelor of Science Degree in Criminal Justice Sciences. Chief Bernabei is also a 2003 graduate of Northwestern University School of Police Staff and Command. He has had of 2000 hours of law enforcement continuing education.

In September of 1981 at the age of 20, Chief Bernabei was sworn in as police officer for the City of Spring Valley. At age 20, he was one of the youngest people to ever be sworn in as a city police officer in Illinois history.

Over the next 10 years, Chief Bernabei was privileged to serve as a police officer in Spring Valley, Illinois, southwest suburban Crest Hill, Illinois and then he served as member of the Bradenton, Florida Police Department from 1986 to 1991. It was with BPD that he served as a street officer, major crimes detective specializing in homicide and child abuse cases as well as a supervisor holding the rank of Corporal assigned to the uniformed patrol division. While in the detective division, he also served as acting Detective Division Commander. In 1989, he was named Police Officer of the Year, an annual prestigious award given by the Bradenton Elks Lodge 1511.

In 1991, Chief Bernabei was offered an opportunity by former Spring Valley Mayor James Narczewski to return to the Illinois Valley area to serve as Chief of Police with the Spring Valley Police Department. He then spent the next 15 years leading that agency transforming it into a 21st century modern full service police agency and helped preside over the construction of a new municipal city hall and police department.

It was in 2006 that Chief Bernabei was recruited by the late Mayor Donald L. Baker to join the City of Peru as Chief of Police. He was also appointed Chief of Police by Mayor Scott J. Harl in 2009, 2013, and 2017 being privileged to be able to lead arguably the finest law enforcement agency in northcentral, Illinois.

Chief Bernabei's commitment to the City of Peru Police Department is second only to his commitment to his sons Dominic and Benjamin.