R. Kelly is alleged to have knowingly been infecting people with herpes since 2007. The 54-year-old singer is on trial on charges of racketeering and violating the Mann Act, an anti-sex trafficking law. He has pleaded not guilty to these charges.

On Thursday, R. Kelly’s personal physician of 25 years took the stand to testify about his treatment of the singer’s genital herpes since at least 2007, in support of the prosecutor’s claim.  The singer, whose real name is Robert Sylvester Kelly is alleged to have violated public health laws that require people who have an infectious venereal disease to notify their partners about their diagnosis.

 Kris McGrath, a Chicago-based physician specializing in internal medicine, appeared in Brooklyn federal court under a subpoena. He testified that he suspected Kelly had genital herpes as early as June 2000 because of symptoms the singer had, but a lab test to detect the virus at the time came back negative.

“I did not conclude that he did not have herpes,” McGrath testified, occasionally referring to Kelly’s medical records, which prosecutors obtained through a subpoena. And he said he told the singer to “inform your sexual partners so they can make a decision whether or not to have sex with you.”

McGrath said it is recommended to treat genital herpes with a drug known as Valtrex, which can be prescribed for short-term treatments. But if a patient has outbreaks of the disease more than three times a year, McGrath testified, it is recommended that the patient take the medication every single day. McGrath said Kelly or his associates would frequently call him for more refills of Valtrex at a Walgreens pharmacy. “It was so often that I had memorized the number to that Walgreens,” he said, and recited the phone number in court, CNN reports.

However, the first documentation of McGrath prescribing the drug was in March 2007. And the earliest record showing Kelly had a history of genital herpes was made in a medical record in 2011. This McGrath testified was done when his office transitioned from paper medical records to electronic ones.