A handful of skilled private detectives/investigators work with defense attorneys on capital punishment and other criminal defense cases. Many are insurance investigators who investigate suspicious claims. Before the advent of no-fault divorce, many private investigators were hired to search out evidence of adultery or other conduct within marriage to establish grounds for a divorce. Despite the lack of legal necessity for such evidence in many jurisdictions, according to press reports collecting evidence of adultery or other "bad behaviour" by spouses and partners is still one of the most profitable activities investigators undertake, as the stakes being fought over now are child custody, alimony, or marital property disputes.
Most jurisdictions require a clean criminal record at the licensing application entry point. When a board of directors exists, it will review an applicant's appeal to determine whether the board can approve the application based on the elapsed amount of time since the last offence was recorded. The board of appeal may approve an application based on good conduct within the last five to ten years.
Private investigators can also be used to perform due diligence for an investor who may be considering investing money with an investment group, fund manager or other high-risk business or investment venture. This could serve to help the prospective investor avoid being the victim of a fraud or Ponzi scheme. By hiring a licensed and experienced investigator, they could unearth information that the investment is risky and or that the investor has suspicious red flags in his or her background. This is called investigative due diligence, and is becoming much more prevalent in the 21st century with the public reports of large-scale Ponzi schemes and fraudulent investment vehicles such as Madoff, Stanford, Petters, Rothstein and the hundreds of others reported by the SEC and other law-enforcement agencies.
PIs also engage in a large variety of work that is not usually associated with the industry in the mind of the public. For example, many PIs are involved in process serving, the personal delivery of summons, subpoenas and other legal documents to parties in a legal case. The tracing of absconding debtors can also form a large part of a PI's work load. Many agencies specialize in a particular field of expertise. For example, some PI agencies deal only in tracing. There are a handful of firms that specialize in technical surveillance counter-measures (TSCM), sometimes called electronic counter measures (ECM), which is the locating and dealing with unwanted forms of electronic surveillance (for example, a bugged boardroom for industrial espionage purposes). This type of niche service is typically conducted by those with backgrounds in intelligence/counterintelligence, executive protection, and a small number from law enforcement entities whose duties included the covert installation of eavesdropping devices as a tool in organized crime, terrorism and narco-trafficking investigations. The best known of these firms in the U.S. include Granite Island Group, Confidential Research & Investigations LLC, Murray & Associates,SLC Security Services LLC and TSCM/Special Operations Group Inc. Other PIs, also known as Corporate Investigators, specialize in corporate matters, including anti-fraud work, loss prevention, internal investigations of employee misconduct (such as EEO violations and sexual harassment), the protection of intellectual property and trade secrets, anti-piracy, copyright infringement investigations, due diligence investigations, malware and cyber criminal activity and computer forensics work. Some PIs act as professional witnesses where they observe situations with a view to reporting the actions or lack of them to a court or to gather evidence in anti-social behavior.
An undercover investigator, undercover detective, or undercover agent is a person who conducts investigations of suspected or confirmed criminal activity while impersonating a disinterested third party. Undercover investigators often infiltrate a suspected insurgent group, posing as a person interested in purchasing illegal goods or services with the ultimate aim of obtaining information about their assigned target.
Many undercover investigators carry hidden cameras and recorders strapped to their bodies to help them document their investigations. The period of the investigation could last for several months or, in some extreme cases, years. Due to the dangerous nature of the job, their real identities are kept secret throughout their active careers. Economic investigations, business intelligence and information on competitors, security advice, special security services information, criminal investigation, investigations background and profile polygraph tests, are all typical examples of such a role.
Private investigators in the United States are licensed or registered by the professional licensing authority or State Police of the state they are located in. Licencing varies from state to state, it can range from just applying for a city business licence in one state such as Idaho, Mississippi or South Dakota, all three of which have no state or local licencing requirements; to needing several years of experience and licencing related training classes and testing in another state, such as Virginia which has one of the highest standards among the states. In general companies offering investigation services must hold an agency licence and all their investigators or detectives must hold individual licences or registrations. There are a few reciprocity agreements that allow a detective working in one state to continue his work in another for a limited time without getting a separate licence, not all states participate in these agreements.