Detectives play an important role in criminal justice. In a big-picture view, they work to gather facts and evidence. Dig down deeper, and you’ll find that detectives might examine records, interview suspects and witnesses, provide video or photo evidence of misdeeds or crimes, and apprehend criminals.

In general, there are two types of basic detectives: public and private. Within these two broad categories, however, there are many other types of detectives with varying specialties. Understanding the nuances between the many different types of detectives can help ensure you hire the right professional for your case, so you can get the results you’re looking for.

Here are nine different types of detectives and their responsibilities:

Type #1: Public Detectives

Any types of detectives in law enforcement would fall under the public detective category. These detectives start out as police officers and eventually rise up to the role of detective. They exchange their police uniforms and police cars for plainclothes and unmarked vehicles. They investigate suspected or actual criminal activity. They’re considered “public” detectives because they are paid with government funding and from public taxes.

These police detectives are considered criminal investigators and they investigate crimes such as assault, burglary, fraud, vandalism, robbery, arson, and homicide.

A police detective’s typical duties include collecting and bagging crime scene evidence, interviewing witnesses, victims, and suspects, and testifying in court. They will follow leads, attend autopsies, perform surveillance, and keep detailed notes of their investigations for the case files.

Type #2: Private Detectives

Private detectives are also known as private investigators or PIs. These professionals aren’t part of the police force and can be hired privately by citizens or corporations for investigative work. While they do not have the powers of law enforcement, they can legally conduct background checks; obtain and provide information on businesses or people; search for offenders or missing persons; and search for missing property, among other things. They cannot make arrests (other than a citizen’s arrest), impersonate police officers, wiretap conversations, or trespass.

Private detectives help fill a need in the community for investigative work that is considered outside the mandate for public detectives.

Type #3: Undercover Detectives

This type of investigator conducts covert investigations to gather evidence in suspected or confirmed criminal activity. An undercover investigation may also be used to gather evidence on competitors or to get special security services information. The detective takes on a different identity to do this work, such as posing as a person looking to purchase illegal goods or services.

Undercover investigators often use hidden recorders and cameras, and the work can last for months or even years.

Type #4: Missing Persons Detectives

Both public and private detectives may specialize in finding missing persons. Often, when resources are limited in the police force, private investigators are called on to continue the search, especially when there is no evidence of foul play in the case. Families often hire these private detectives when they do not believe their case is a priority with the police.

Private detectives have also been commonly used to find a parent or child in the case of adoption, when either party wishes to meet the other. Tracking down the birth parents or children can take considerable effort, and private investigators have the resources to get the job done.

Type #5: Missing Property Detectives

Your items may mean a lot to you, but unless they’re very expensive, your property might not be a priority for the police. In this case, you might want to hire a private investigator to recover your lost or stolen property, such as a stolen car or missing jewellery.

Type #6: Insurance Claim Detectives

These types of detectives work for insurance companies to investigate possible cases of fraud, including fraudulent worker’s compensation claims. Other claims that are commonly investigated include injuries, property damage, medical issues, and liability. In these cases, the detective would conduct background checks on claimants, review the circumstances surrounding the claim, interview witnesses, and perform surveillance.

Type #7: Due Diligence Detectives

Many corporations hire private detectives to conduct due diligence investigations. In this case, the investigator is called upon to conduct research when high-risk investments or business ventures are at play. A detective can uncover a Ponzi scheme or fraudulent company that can put their client’s money and reputation at risk.

Type #8: Homicide Detectives

You see many homicide detectives on TV. When a murder is committed, homicide detectives are called to the scene to investigate. These investigators are public detectives and are critical members of law enforcement. They look for clues and leads, analyze the scene and the evidence, and even solve cold cases.

Type #9: Forensic Detectives

This public investigator uses science to solve crimes. In forensic science, biology, chemistry, and physics are used to recognize, identify, and evaluate physical evidence. Using their scientific knowledge, forensic detectives help solve crimes by determining when and how crimes occurred. They collect and analyze evidence like weapons, written notes, fingerprints, and bodily fluids.

This solid scientific evidence holds up well to scrutiny in court and can help prove or disprove a suspect’s guilt beyond a shadow of a doubt.