How to become a detective

1. 1Meet the basic hiring standards

   Time: Before applyingSources 1

   Police departments usually require applicants to be at least 21 and to meet strict physical and personal standards; a felony conviction or drug use can disqualify you. Each department adds its own rules, so read the posting closely. Some departments run cadet programs for 18-to-20-year-olds. Keep your credit, driving and social media history clean, because background investigators look at all of it.

2. 2Get college credits or a degree

   Time: 0-4 yearsCost: $9,645/yr median public in-state tuition (criminal justice)Sources 1, 5

   A high school diploma is the minimum, but many local applicants have college coursework, some departments require it, and some departments want a bachelor's degree before promoting officers to lieutenant or higher. Criminal justice is common, but accounting, computer science, foreign languages and law are especially useful for fraud, cyber and federal investigations. The FBI and many federal agencies require a bachelor's degree.

3. 3Pass the hiring process and the police academy

   Time: Several monthsCost: Usually paid by the departmentSources 1, 6

   Hiring includes a written exam, physical fitness test, interviews, a background investigation and often polygraph, psychological and drug tests. Academy training covers state and constitutional law, civil rights, ethics, patrol, firearms, defensive tactics, first aid and emergency response. Each state's Peace Officer Standards and Training (POST) agency or equivalent board sets minimum academy training, and many also give a certification exam.

4. 4Work patrol and finish probation

   Time: Usually less than 5 yearsCost: Paid workSources 1, 2

   New officers ride with a field training officer, then work patrol on their own through a probationary period. Patrol is where you learn to write solid reports, handle scenes, interview people and testify. Officers who want to investigate should volunteer for follow-up work, take investigation courses and build a reputation for thorough reports, because supervisors weigh these when choosing detectives.

5. 5Earn a detective or investigator assignment

   Time: Varies by departmentSources 1

   In large departments, officers become detectives through a promotional exam and interview, or by being selected for an investigative unit. Smaller agencies may assign the job based on experience and performance. Once in the unit, new detectives learn case management, interviewing and interrogation, search warrant writing and digital evidence from senior investigators and specialized courses.

6. 6Federal route: apply to become a special agent

   Time: Hiring can take up to a year, then academy trainingSources 3, 7, 8, 4, 1

   FBI special agents must be U.S. citizens, at least 23 and younger than 37 at appointment (some veterans can get an age waiver), and hold a bachelor's degree with qualifying work experience. Since July 6, 2026, a bachelor's plus one year as a sworn officer, or an advanced degree, qualifies at a new GL-9 level. New agents train for 18 weeks at Quantico, Virginia. Many other federal agencies send investigators to the 59-training-day Criminal Investigator Training Program at FLETC in Glynco, Georgia.

Programs, tuition and graduates’ earnings

U.S. Department of Education, College Scorecard (most recent cohorts, released 2026-10-15). Scorecard groups programs by 4-digit field, so a row can include related programs. Tuition is the median published undergraduate tuition and fees of the colleges offering the program (shown only for undergraduate credentials); debt is the median of programs’ median federal loan debt at completion; earnings are the national median for the field and credential four years after completion.

Requirements differ by state. Check your state’s rules in the CareerOneStop License Finder (U.S. Department of Labor) before you enroll.

Interviewing

Most cases turn on what victims, witnesses and suspects say, and getting accurate statements without contaminating them takes practice.

Report and warrant writing

A judge signs a warrant and a prosecutor files charges based on what you write, so gaps or errors can sink a case.

Attention to detail

Small inconsistencies in timelines, phone records or evidence logs are often what break a case open or get it thrown out.

Emotional resilience

Detectives deal with violent deaths, abused children and grieving families, sometimes for months on the same case.

Knowledge of criminal law and procedure

Searches, interrogations and evidence handling must follow constitutional rules or the evidence can be thrown out in court.

O*NET 31.0 rates these skills as most important for the occupation: active listening, speaking, critical thinking, reading comprehension, writing.

Training cost

$0–$38.6K

Before financial aid

Time

About 5 years after joining a police department

Typical path

Median pay

$93,790

All US jobs: $50,980

Payback once qualified

Under 1 year

Pay above the all-jobs median vs. cost

Low: $0 when a department hires you with a high school diploma and pays for the academy, which is common. High: 4 years x College Scorecard median public in-state tuition for criminal justice bachelor's programs, $9,645 = $38,580, the education needed for the FBI and many federal agencies. Not included: self-paid academy tuition in states that allow it, books, living costs and private-college tuition.

Rough guide only: ignores taxes, aid, interest and earnings given up during training. How we calculate it.

• Detective sergeant or lieutenant

  Promotion depends on written exams and job performance, and some departments want a bachelor's degree for lieutenant or higher ranks.

• Forensic scientist$72,060 median

  Investigators interested in evidence analysis can move into crime lab work, which requires a bachelor's degree in a natural science such as chemistry or biology.

• Private investigator$51,220 median

  Retired detectives often open or join private investigation firms, which usually requires a state private investigator license.

• Lawyer$159,670 median

  Some investigators go to law school and become prosecutors or defense attorneys, which takes a bachelor's degree, 3 years of law school and the bar exam.