Originally Posted by digitalgravy
Is there a way to find out which member in a group was the last person to modify a file?
Modify in what way? Anyway. In general, out of the box setup, no. Not unless you specifically log that kind of details for auditing purposes. You could try and correlate MAC times with system logs, user login data and history to arrive at "circumstantial evidence" but the more concurrent logged in users modifying the file the less chance you have.