John Cook is a teenage hacker responsible for sabotaging the Hogan-Hayes Diabetic Clinic computer and increasing the insulin dosages of several patients, which killed two of them and left seven more in comas.
John's father Robert hated the medical system for not treating his diabetic retinopathy, which was incurable. His obsessive hatred led to him divorcing his wife, which triggered John into committing the sabotage. The evidence against John was thrown out, so Robert was tried instead to pressure John into confessing, which eventually worked.
John pleaded guilty to two counts of second-degree murder and was sentenced to 25 years to life in prison (L&O: "Virus")