Many private detectives/investigators with special academic and practical experience also work with defense attorneys on capital punishment and other criminal defense cases. Many others are insurance investigators who investigate suspicious claims. Before the advent of no-fault divorce, many private investigators sought 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 spouses' and partners' adultery or other "bad behaviour" is still one of their most profitable undertakings, as the stakes being fought over now are child custody, alimony, or marital property disputes.
Private investigators can also perform due diligence for an investor considering investing with an investment group, fund manager, or other high-risk business or investment venture. This could help the prospective investor avoid being the victim of a fraud or Ponzi scheme. A licensed and experienced investigator could reveal the investment is risky and/or the investor has a suspicious background. This is called investigative due diligence, and is becoming 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 Securities and Exchange Commission along with other law enforcement agencies.