Patricia Hilliard Robertson was born in Indiana, Pennsylvania on March 12, 1963, to parents Harold and Ilse Hilliard. Her father was involved with international construction, which allowed Hilliard to travel in her childhood. During her early years, she spent time in her mother's native Indonesia. After growing up in Homer City and graduating from Homer Center High School in 1980, she went on to earn her bachelor of science in biology from Indiana University of Pennsylvania in 1985.

After earning a medical degree from the Medical College of Pennsylvania in 1989, she began a three year residency in family medicine. Upon completion of her residency in 1992, she was certified by the American Board of Family Practice. She would later marry Scott Robertson and earn her pilot's license from Dr. David Dulabon, a urologist and flight instructor, while living in Erie. In 1992, Robertson joined a group practice and worked at St. Vincent Hospital as the clinical coordinator for medical student training. She also trained and supervised resident physicians at that time. Working as a family practitioner at the Elk Valley Medical Center in Girard, Pennsylvania, until 1995, Robertson left Pennsylvania with dreams of outer space.

In 1995, Robertson earned and began a two year space medicine fellowship at the University of Texas Medical Branch and NASA Johnson Space Center. She was one of two students selected for the fellowship, and during her time she researched "eccentric and concentric resistive exercise countermeasures for space flight," according to a May 2001 NASA profile. During her fellowship, Robertson also worked on staff as a member of the Emergency Medicine and Department of Family Medicine. She completed the fellowship, which include the aerospace medicine primary course at Brooks Air Force Base, in 1997. In 1998, after completing her fellowship, Robertson served as chairman to the Bone, Muscle, and Exercise Integrated Product Team at the NASA Johnson Space Center's Flight Medicine Clinic. In June of that same year, Dr. Robertson was selected by NASA as an astronaut candidate and eventually began training in August.

As a mission specialist candidate, Robertson's training included many orientations, scientific and technical briefings, as well as major preparation and instruction on International Space Station and Shuttle systems. In preparation for T-38 flight instruction, Robertson also was versed in the areas of ground and physiological training in addition to wilderness and water survival skills. Dr. Robertson was assigned to the ISS Expedition 2 Crew, as a crew support astronaut and office representative for the Crew Healthcare System. Serving as a communication liaison between the Astronaut Office and the Mission Control Flight Control Team, Robertson would attend meetings to represent members of the Expedition 2 crew. As a support astronaut for the Expedition 2 crew members on board the International Space Station, Robertson would also coordinate activities for the crew and assist with communication between the astronaut crew and NASA's staff and technicians.

While at NASA, Dr. Robertson received the NASA Performance Award. She also received the Young Investigator Award from the Aerospace Medicine Association. She was involved with the Aerospace Medicine Association, Aircraft Owners and Pilots Association, American Association of Family Practice, Experimental Aircraft Association, and International Aerobatic Club. On May 22, 2001, Dr. Robertson sustained severe injuries in a private plane crash at Wolfe Air Park in Manvel, Texas, about twenty miles south of Houston. The owner and pilot of the single-engine experimental plane, forty-six-year-old Roy Mack Paul Adams, and Robertson were practicing touch-and-go landings. According to the Federal Aviation Administration (FAA) on the pair's fourth take-off, the plane shifted to the right and the left wing scraped the runway which caused the plane to somersault down the landing strip. Finally, striking a plot of trees, the plane caught fire. Robertson and Adams were engulfed in flames when they emerged from the wreckage and a nearby witness quickly drenched them with a fire extinguisher. Both Robertson and Adams were taken to Memorial Hermann Hospital in Houston; Robertson had second and third degree burns covering 90 percent of her body.

On May 24, 2001, Dr. Robertson died due to her severe injuries; she was thirty-eight at the time. The following day, flags were flown at half staff at the Johnson Space Center. Though she was residing in El Largo, Texas, at the time, Robertson was buried in Pennsylvania. Dr. Robertson was survived by her husband, Scott Robertson, her mother, Isle Hilliard, older brother, Tim Hilliard, and two younger brothers, Scott Hilliard and Keith Hilliard. Though she had not yet been to space at the time of her death, family members said she had been assigned a spaceflight mission for the following year. The multi-engine flight instructor had accumulated more than 1500 hours of flight time before her death. Following Robertson's death, a live oak tree was planted in her memory at the Johnson Space Center's Memorial Tree Grove, a memorial which honors past Houston astronauts and NASA officials.