“The person(s) in charge of a clinical trial or a scientific research grant. The PI prepares and carries out the clinical trial protocol (plan for the study) or research paid for by the grant. The PI also analyzes the data and reports the results of the trial or grant research. Also called principal investigator.”
The former "Principal Investigator" of the (research) project. Often the professor who is responsible for obtaining the grant and driving progress
principal investigator
The private investigator with whom you have severed ties.