Lieutenant Douglas P. Bernabei began his law enforcement career in 1978 with the Spring Valley Police Department as 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. Lieutenant Bernabei is also a 2003 graduate of Northwestern University School of Police Staff and Command. He has had over 2000 hours of law enforcement continuing education.

In September of 1981 at the age of 20, 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, 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, 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 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.

During his tenure as Chief of Police the Peru Police Department became one of the most well-staffed, well equipped, well-trained, well-paid agencies in all of downstate Illinois. While serving as Chief of Police he introduced the first ever police K-9 units in city history, presided over the construction of a state-of-the-art police firing range recognized as one of the nicest range facilities in Illinois. Bernabei also introduced a take home car program whereby neighborhoods in the city have marked squad cars parked  in residential areas when officers are not on duty creating both a sense of security for residents and also serving as a crime deterrent, created the Special Investigations Unit dedicated to drug enforcement in the city resulting in a record number of arrests and record seizures of cash approaching million dollars. In 2015 Bernabei also assumed leadership of the State of Illinois mandate creating regional dispatch centers and was elected the first ever Chairman of Illinois Valley Regional Dispatch Center and for several years served as executive director of Illinois Valley Regional Dispatch serving the people of LaSalle, Peru, Oglesby, Mendota Spring Valley, Earlville and Utica.

In his final year as police chief the department moved into a new modern state-of-the-art police headquarters that will serve the Peru community for generations to come. During his tenure the City of Peru enjoyed a 56.48 % reduction in crime.

From 2014 to May of 2021 Bernabei also served in a dual role as the Administrative Services Manager with the city having administrative oversight of all city departments.

On September 1, 2021, Bernabei assumed duties as the Lieutenant of Administrative Services for the Peru Police Department.

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