IONIA, Mich. (WOOD) — An Ionia therapist accused of sexually abusing a patient and billing insurance for sessions where no counseling happened.

Derek Robertson, 50, of Lowell pleaded guilty Tuesday to health care fraud, delivery of a controlled substance and fourth-degree criminal sexual conduct.

Several additional counts were dismissed under the terms of a plea agreement.

The CSC charge stemmed from the alleged sexual relationship between Robertson and his patient that state investigators said lasted for nearly a year and a half. In Michigan, it’s illegal for mental health professionals to have sex with clients, regardless of consent. The state also says Robertson admitted that he continued to bill the woman even when they only had sex during appointments.

In late March, Viewpointe Counseling in Ionia posted on Facebook confirming Robertson no longer worked there. His license was suspended in April. He was formally charged in May.

Sentencing has not yet been scheduled.