Detectives investigate all types of cases, but the most challenging and complex are unsolved crimes that were committed in the past. These investigations–called cold cases because they have been dormant for long periods of time–may stretch back for decades, but they are now being resurrected and solved thanks to advanced DNA testing and new investigative techniques. If you think you have what it takes to join this high-profile profession, you’ll need training and credentials--and you’ll have to pay your dues before moving into the elite ranks of cold case detectives. But ask those working in this fascinating field, and they'll tell you it was worth all the time and effort.

Take the Law-Enforcement Track

Get a degree. Being accepted into the ranks of your local police or sheriff’s department means you’ll be competing with individuals with degrees, so strike a level playing field by earning the credentials needed to do the job right. Major in either criminal justice or science and minor in the other to give you expertise in both disciplines.

Attend the police academy. Police academies train men and women to handle everything from domestic disturbances to disasters by exposing trainees to a combination of classroom learning and hands-on experience. Certification from a police academy plus a degree can help speed the advancement of upwardly mobile law-enforcement professionals.

Find a job. Every law-enforcement agency is unique, with specific recruitment needs and rules. Some require staff to live within city limits to qualify for employment, while others have no education requirements. Sample various departments by visiting agency websites in your community. If you land an interview, ask up front whether or not the agency has a cold case department. Not all do. Tight staff numbers and overly burdened budgets can put special interests, like a cold case squad, on the back burner.

Advance through the ranks to gain experience in multiple departments. Sampling narcotics work, missing persons, homicide, vice and other casework adds to one's basic education. Experience in day-to-day operations, policies and protocols builds credibility and primes the best of the best for advancement. A broad range of experience will help put you on track for job openings on cold case squads.

Take the Military Track

Advise your recruiter of your interest in law enforcement. The time to strike a deal to get the training assignment of your choice is at the recruitment stage. If you have college credits in criminal justice, this can help make your case for a military law-enforcement assignment.

Serve your tour of duty. Succeed in being assigned to military-police training after boot camp, and you will increase your chances of having a cold case career in civilian life. Four years of experience in the military police looks great on a resume, and can push your candidacy ahead of that of someone with a degree but no hands-on experience.

Shop around before choosing a job. All branches of law enforcement are looking for candidates, so don’t restrict yourself to a single agency. Apply to police, sheriff, FBI and comparable state-based agencies. Investigate each to make certain there’s a cold case division to which you can transition or use the job as a stepping stone.

Take the Private-Detective Track

Receive some law-enforcement training. Both college and the military are great jumping-off points for becoming a private detective. Professionals recommend cutting your teeth as an employee for an agency before you go off on your own. Be certain the agency you choose is familiar with and has handled cases that involve cold case investigations.

Apply for your license, gun-carrying permit and other state-mandated documentation. Every state requires private detectives to be licensed. Expect to take written exams and be tested on weapon use and other skills. You may need to get security clearances. Register your credentials with databases that allow you to do criminal background checks and gain access to sites that store confidential information unavailable to the general public.

Become self-employed. You’ll get the most amount of work if you launch your solo career as a generalist, handling everything from domestic surveillance to child recovery, and from insurance fraud to industrial espionage. When your client base is secure, move to your specialty and advertise yourself as a cold case specialist, helping to find answers to old but not forgotten crimes.