As law enforcement officials comb through medical records to determine who supplied and administered the anesthesia Propofol and other drugs to Michael Jackson, we've learned there may be a fail-safe way of getting at the truth.

It's no secret -- especially in a celebrity town like L.A. -- some doctors use pseudonyms for celebrity patients and sometimes their medical charts somehow get "lost." But we've learned most doctors leave an indelible footprint when it comes to treating patients.

Many doctors -- especially ones with big practices -- use medical software systems from MD Systems, NexTech and other companies. These companies provide the software that makes it easy to input billing data.

Doctors typically input the patient's name, billing amount, type of treatment, type of drugs prescribed and administered, and date of service. Here's the thing -- that data cannot be deleted from the server.

The system allows doctors to add other data like medical charts, and those things can be deleted. But if someone deletes that info, the software shows the name of the user who did it and the date it was done.

Bottom line -- the basic billing information will not go away.