You may be thinking that the only way you can obtain a persons financial information is through a court ordered subpoena duces tucem or by police though a search warrant. This is not true, in many cases as long as you have a legal and permissible reason to need this kind of information a private can legally investigate and obtain it for you. This can be done in compliance with all applicable laws such as the 1999 Gramm-Leach Bliley Act.
In many cases a private investigator can use an asset search investigation to discover a great deal of banking and financial information without having to subpoena. An asset search investigation when conducted by a professional with many years of experience can recover a great deal of financial and even banking information about a person. Of course one you have identified which institution the subject is banking at a subpoena can be used to obtain actual bank statements, records and deposits, withdrawals etc.
If you are in need to obtain banking and financial information about a person your first call should be to a private investigator that is experienced in asset search investigation. A standard, basic asset search can locate bank accounts, property, real estate, vehicles and much more financial information about a person. Once you have this information you can use the subpoena process to serve each institution located to turn over all records relating to your court case.
It may be difficult to find an investigator that has expertise in this area. Not every investigator will do asset searches. It's a specialized field of investigation. Also recent legislation has made it unlawful to use the old standard techniques the private detectives used to use to obtain this kind of financial information. In fact some investigators are so inexperienced in this are that they mistakenly believe that any kind of investigation to disconcert financial information about a person is unlawful or illegal. This is simply not true.
A very basic search of public records such and real property records can reveal banking information about a person. Property records are public information that anyone can view without any kind of subpoena or court order. Many times this recorded document will include first and second mortgages associated with the property. This will reveal banking information that a trained investigator can follow up on, legally without a subpoena, and return financial banking information about the person being investigate.
Now this is just one very simple obvious method that anyone can do. But keep in mind that a professional investigator that has been doing this for years has literally hundreds of such avenues of perfectly legally obtainable financial information that does not initially require a court order or subpeona duces tucem. Anyone that tells you it is illegal or unlawful to obtain financial information about a subject without a subpoena is simply misinformed. They are acting on old outdated misinformation.