We are based and experienced in Australia and we can only talk about practices and rules in Australia and not other countries.
IMPORTANT WARNING:. There are some private investigators in Australia including a couple of so-called high-profile operatives that have very dubious background and have been subject of police investigations, licence cancellation and endless complaints to trade agencies. These PIs (or rather, pretend-PIs) will assure you they can access all the things we explained below that cannot be done. They will tell you they have the right connections and if you believe it, then you're in for some surprises. What they will do is take a good chunk of your money (hundreds or thousands) and at some stage get back to you and say no, no trace, nothing negative found. But sorry, we had to spend your fee to pay off the informers. Believe it? Doesn't matter, because you are not going to complain to police about soliciting a PI to illegally access confidential police, tax office or social security records, are you? And these crooked PIs know it.
Typical question #1: my partner is using his mobile to speak to a woman behind my back. How can I get the details of the calls or texts?
Answer: You can have the SIM card read, but only if it's yours. Otherwise it's against the law. You cannot get access to phone records of any kind from networks.
Typical question #2: I know he's seeing a woman when he's away on a trip. Can we track his car with one of those electronic tracking devices?
Answer: You can't in NSW and Victoria as the law says you must have consent from the person using the vehicle. In other states the law is less clear about it and it may be possible to legally use a tracking device. But can you be sure?
Typical question #3: I have an internet relationship and am thinking of starting a new life with this person. I want to know what bank accounts he has and what debts he has. I also want to know if he has a criminal record, if he has children and if he has ever been married. Can you access the records?
Answer: No, you can't. All such records are strictly protected in Australia.
Typical question #4: I need a private investigator to bug a phone for me. How much will that cost me.
Answer: probably a few years jail. It is against the law to bug a phone be that by directly wiring into the phone line or by using a wireless transmitter. You won't find a private investigator to bug a phone, you need a criminal.
Typical question #5: My ex-wife moved away with our child. She has custody, but I want to speak with her and she hasn't left any contact details. I know she's collecting sole parents benefits, how much to check social security records or drivers licence records?
Answer: Such records cannot be checked.
Typical question #6: I met a guy on a flight into Sydney recently, but didn't get his full name or contact details. Can you look up the passenger lists for the flight? I have the date and the flight number.
Answer: Not possible, such records are strictly protected.
Most people presume that the primary function of a private investigator is to access records and that somehow an investigator has access to restricted or secret records which normal people don't have access to. The prevailing presumption is that 'finding out' means primarily looking up some confidential databases.
A skilled, experienced private investigator can probably find out most of the information sought in these typical questions, but he or she won't be doing it by accessing restricted records. An investigator cannot access any records that you cannot access, the investigator has no special authority or privileges under the law. The PI licence does not bestow any special rights, just obligations.
What the private investigator does usually have is imagination, ingenuiety, persistance and the gift of the gab. The PI will find out most of the time, most of the things you want by extracting from the client any potential lead and then going about visiting locations and chatting with people or watching people. The PI will also access legal records, records that you too can access, except the PI is better experienced how to do it and where to find it. It is in the way the PI will chat to people, in the ingenious ways he will look for leads, that will lead him to information.
There are many records that the private investigator can indeed check, but you too can check them. Such records are: ASIC company and business records which can reveal of the person you are seeking is or was involved in a business; Land Titles Office (in your state) to find out whether the person owns, is purchasing or used to own propery; Office of Fair Trading (consumer affairs) records, bad tenants records, local council records; court transcripts; and bankruptcy records.
The records that are not accessible about individuals are: credit reports, drivers licence records, motor vehicle registration records, telephone records, criminal records, bank and financial institution records, Centrelink records, tax records and records held by the Office of Births Deaths and Marriages. In certain circumstances a couple of these records can be accessed with an explicit written authority from the subject of the search.
You might come across websites that offer criminal records checks, however, their records are not derived from actual police databases, but a variety information collated from various sources including newspaper reports and court transcripts. Such information is incomplete and not necessarily authenticated. It means that such a site might tell you "no criminal record found for Joe Bloggs" but that will not be proof that Mr Bloggs does not have a criminal record.
If you want to find out something ask the investigator what he or she can do. If the PI all too readily assures you of successful outcomes and an ability to access all kinds of records, beware. An ethical private investigator will plainly tell you what cannot be done and won't promise successful outcomes.
The only thing the PI should promise you is to be diligent and honest.