I cannot confirm this through personal observation or knowledge based on research, but I have been told that my family believed in using private detectives to obtain information about people and things.
The only P.I. I ever knew well personally was a colleague of mine at the insurance company. His job was to ferret out fraudulent claims by photographing people who claimed severe injury, or even paralysis, dancing at weddings, and uncovering other forms of deceit. He was a curious fellow, uniquely entertaining, unlike the grimmer police detectives I met working as an Assistant D.A. in Brooklyn.
I have no interest in ever engaging a private detective's services. But I believe I would be a good P.I. if I tried my hand at it and that Caroline and Jane would be equally adept. I would love to see our names written backwards across a broad glass window.
John Cale: Evidence (Link)