Krista Sivertsen was a female Human in the 23rd century. She was a student of Dr. Leonard McCoy's in the 2250s or early 2260s, and eventually earned a doctorate in psychiatry.
In 2284, she worked in the Psych Division at Starfleet Medical, and that year performed a psychoscan on Admiral James T. Kirk, at McCoy's request. She discovered several abnormalities, seemingly brought about by a reading of the book Strangers from the Sky, which pointed to a form of schizophrenia, and suggested that he be hospitalized. After several days of ineffective treatment, Sivertsen was approached by Captain Spock, who presented identical psychoscan readings to Kirk's. At Spock's instance of using a mind meld with Kirk to find the root of their problems, Sivertsen reluctantly released both to the care of McCoy. (TOS novel: Strangers from the Sky)
- It's unclear exactly when or where McCoy had been Sivertsen's teacher, though he was still married at the time. Though it is not explicitly stated, Sivertsen was likely a Starfleet officer, which suggests McCoy had taught her at Starfleet Academy.