The coroner has ruled Jackson's death at age 50 was a homicide caused by acute intoxication by the powerful anesthetic propofol, with other sedatives a contributing factor.
Criminal attorney J. Michael Flanagan said Friday he had been hired to join Houston attorney Edward Chernoff in representing Murray.
Flanagan previously worked in the media spotlight representing Britney Spears in a hit-and-run case. He said he tried a propofol case several years ago, representing a nurse who was acquitted after it was shown she played no role in administering propofol to a patient who died.
Court documents show police who searched Jackson's home the day after he died found several medications and drugs, including marijuana, Valium, and other sedatives.
Murray, 56, has acknowledged giving Jackson two of the drugs cited in the coroner's report.
To prove a charge of involuntary manslaughter, authorities must show there was a reckless action that created a risk of death or great bodily injury. If a doctor is aware of the risk, there might also be an issue of whether the patient knows that risk and decided to take it.
An involuntary manslaughter conviction carries a potential sentence of two to four years in prison.
Murray is currently practicing medicine at a clinic in Houston.
The Associated Press contributed to this report.