What Does a Criminal Investigator Do?
Criminal investigators, also called CIs, play an integral role in the justice system. They gather facts and collect evidence to help solve crimes.
Their skills make them well-suited for a wide variety of jobs. They may work for a city or county police department, the state, the FBI or another federal law enforcement agency. Their roles vary depending on federal, state or local laws. They may also be specialists, focusing on forensic science or a specific type of crime.
Some investigators track down information on computers, while others spend more time in the field. Criminal investigators use the information they gain through their daily work to prepare criminal complaints and testify in court.
Criminal investigative work often involves nights and weekends. This career is rewarding and satisfying, but it can also be stressful because of the situations investigators encounter at crime scenes. Interested? Read on to learn more about what it will take to get there.
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42,000
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146,000
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87,000
8,570+

To a criminal investigator, even the smallest piece of evidence matters. (Credit: Hajrudin Hodzic/Shutterstock)
Job Responsibilities
- Collect evidence at crime scenes
- Interview witnesses
- Analyze evidence and do further research
- Observe suspects
- Write detailed case reports, and file and maintain records
- Obtain warrants and participate in the arrest of suspects
- Testify in court
How To Become a Criminal Investigator: FAQs
What are the requirements to be a criminal investigator?
Candidates for this job have graduated high school and earned an associate degree in criminal justice or law enforcement. Some have earned a bachelor’s degree.
Community colleges and universities offer programs, which include courses in criminal law, criminal theory and psychology.
Most graduate from a police training academy and work as police officers to gain law enforcement experience. Training academy work typically includes classes, such as suspect apprehension, and hands-on work, such as traffic control, incident reporting and weapons training. Some programs also include a physical fitness component.
Job candidates with the ability to speak more than one language have an advantage.
Investigative work involves a lot of on-the-job training as each case hones knowledge and skills. Some agencies require investigators to earn continuing education credits, but it varies widely.
What other qualifications do I need?
There are different age and training requirements for city, state and federal jobs for detectives and criminal investigators. Most agencies require candidates be 21 years old and a U.S. citizen with a valid driver’s license and no felony convictions. Some agencies will require specific certifications, a background check, drug testing and a psychological exam.
Employers look for candidates with previous experience, which can include military service or work as a police officer or correctional officer. That’s why many officers serve on the police force in another capacity before earning a promotion to criminal investigator. (For more information on how to prepare, read How to Become a Police Officer.)
It’s worthwhile to get the perspective of someone who has done the job, such as Donald Martin (see above) and the Coweta County Sheriff’s Office investigator in this video.
How long does it take to become a criminal investigator?
An associate degree takes two years to complete, and a bachelor’s degree takes four. Police academy typically takes six months and is followed by a probationary period of six months.
What’s the outlook for this profession?
Police and detective employment opportunities are expected to grow 7% from 2020 to 2030, according to the Bureau of Labor Statistics.
What skills and qualities would make someone a good fit for this job?
- Excellent communication skills
- Strong critical thinking skills
- Good decision-making skills
- Empathy and the ability to understand the perspectives of many types of people
- Trustworthiness and high ethical standards
The bottom line:
This is a career that satisfies a sense of adventure plus a desire to help others in the community. Many different agencies need crime-solving skills, so there’s no shortage of possibilities. But getting to those jobs will require hard work and time gaining experience as a police officer. If you’re up for the task, read more below about training opportunities.