A detective is an investigator, either a member of a law enforcement agency or a private person. The latter may be known as private investigators or "private eyes". Informally, and primarily in fiction, a detective is any licensed or unlicensed person who solves crimes, including historical crimes, or looks into records.
In some police departments, a detective position is not appointed, it is a position achieved by passing a written test after a person completes the requirements for being a police officer. Prospective British police detectives must have completed at least two years as a uniformed officer before applying to join the Criminal Investigation Department. UK Police must also pass the National Investigators' Examination in order to progress on to subsequent stages of the Initial Crime Investigators Development Programme in order to qualify as a Detective.
In many other police systems, detectives are college graduates who join directly from civilian life without first serving as uniformed officers. Some people argue that detectives do a completely different job and therefore require completely different training, qualifications, qualities and abilities than uniformed officers. The opposing argument is that without previous service as a uniformed patrol officer, a detective cannot have a great enough command of standard police procedures and problems and will find it difficult to work with uniformed colleagues.
A private investigator (often abbreviated to PI and informally called a private eye), a private detective or inquiry agent, is a person who can be hired by individuals or groups to undertake investigatory law services. Private detectives/investigators often work for attorneys in civil cases. A handful of very skilled private detectives/investigators work with defense attorneys on capital punishment and criminal defense cases. Many work for insurance companies to 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.
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.