Miranda Sevcik, a spokeswoman in Houston for Murray and his lawyer, Edward Chernoff, said the doctor had no comment and reiterated he neither prescribed nor administered anything that should have killed Michael Jackson.
Jackson died at his Los Angeles home in June while under Murray's care as the singer prepared for an ambitious concert schedule.
The district attorney's office is waiting for the Los Angeles police to turn over the case before presenting it to a grand jury.
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.
Before an indictment can be sought, the person said the Los Angeles Police Department will follow the formality of presenting the case to the district attorney.
A large number of witnesses have been interviewed including those who were present during Jackson's last days and those who worked with him in preparation for his comeback concert, "This is It."
Authorities have also lined up medical expert witnesses who will testify about the normal standard of care in a situation such as Jackson's and will give opinions on why Murray's actions constituted gross negligence, the person said.
The investigation was substantially completed by the end of December, the person said.
Murray's professional history is expected to be explored during a trial with an emphasis on whether he had the required expertise in administering the powerful anesthetic propofol which is believed to have killed Jackson.
The timing of an indictment will be dictated by two factors -- how long it takes for the district attorney's office to conduct an internal review of the evidence and when the grand jury will be available to hear the case.
The person said it was thought that it would be more efficient to go to a grand jury than to charge Murray and proceed by way of a preliminary hearing.
A presentation to the grand jury where witnesses testify behind closed doors could take three to five days.
Murray, a cardiologist with offices in Las Vegas and Houston, was hired by Jackson not long before the pop star's death to travel with him on the "This Is It" tour that was to begin in London.
The doctor was with the star in Jackson's rented Los Angeles mansion and tried to revive him when he was found unconscious.
Among the drugs found in Jackson's home was propofol, and a subsequent autopsy found that Jackson died of acute propofol intoxication.
Propofol depresses breathing and the heart rate and lowers blood pressure so it's supposed to be administered by an anesthesia professional in a medical setting.
