Perhaps he wanted to ensure his access to insulin and to Terri in order to bring her down slowly.
Personally I think that his nursing studies were a good story to get a bigger award in damages.
Once anurse with the award in his pocket,he may well have come upon the plan to do that.
I believe there is the affidavit of the nurse that found an insulin syringe in the wastebasket of Terri's room,an injection marks on her body and Terri very lethargic and sweaty. She reported it to the police and was fired promptly.
Why the police did not investigat further is beyond me but the way this is playing out,this is very unsettling.