If Officer Stephanie A. Phillips were to be indicted or convicted, the 17-year police veteran would face disciplinary action, Halstead said.
Jacobs' family had called police that day to report a disturbance because he had not been taking his medication for bipolar disorder, relatives have said. Officers said he became combative.
In August the medical examiner ruled that Jacobs' death was a homicide. Phillips stunned the 24-year-old with a Taser twice — the first time for 49 seconds and the second time for 5 seconds, with a 1-second interval between the shocks, according to the Tarrant County Medical Examiner's Office report.
Neither paramedics at the scene nor emergency room personnel could revive him, and he was pronounced dead about noon — an hour after police used the Taser, the report said.
Tasers issue a 50,000-volt shock that over-stimulates the nervous system and causes muscles to lock up, temporarily immobilizing a person.
An autopsy concluded that the primary cause of death was "sudden death during neuromuscular incapacitation due to application of a conducted energy device," and said no traces of alcohol or drugs, electrolyte imbalances, or signs of heart or lung disease were found — all of which can be contributing factors in a death.
The prosecutor handling the Jacobs case did not immediately return a call Friday to The Associated Press.
Jacobs' family believes that not disciplining the officer is a "true miscarriage of justice," said the Rev. Kyev Tatum, a family spokesman.
"We're saddened, disappointed, disheartened, angry, upset, insulted and offended," Tatum said Friday after hearing about the police chief's comments.
"Michael Jacobs was not a criminal. He was a young man who needed mental help," he said.
Halstead said his officers still use Tasers but that they will get more use-of-force training starting early next year. He said he also consulted with the county's mental health department to learn more about dealing with mentally ill or emotionally disturbed suspects.
Halstead said he voluntarily gave a copy of his department's report to the U.S. Justice Department because he wanted to be "open and transparent." Police Lt. Paul Henderson said it had nothing to do with the family's criticism of the incident or investigation.
In an unrelated case in South Texas earlier this week, a grand jury declined to indict three La Marque police officers over the May death of a man who was subdued with a Taser. The panel had the option of considering murder, manslaughter, criminal negligent homicide or official oppression counts, said Galveston County District Attorney Kurt Sistrunk.
A medical examiner determined Jamaal Valentine's death was caused by high levels of phencyclidine and cocaine, and the report also cited "blunt head trauma during police restraint."
Anyone else find it disturbing that a cop with 17 years didn't know the proper use of force?
No doubt. Just stop to consider how long 49 seconds really is, particularly when running 50,000 volts through someone. Taser just released a notice to law enforcement officials, warning them not to aim for the chest when using a Taser because of the increased risk of a "cardiac event." First time Taser has ever conceded that there is a risk of death associated with the product.
The military actually handles things simularly. Example: Rules of Engagement in Iraq. If you end up shooting and killing someone who is a innocent civilian, you will not get in trouble as long as you can provided a prospective that made them an apparent threat. They told us this going up north from Kuwait that a majority of cases (in the 90+ percent) involving civilian casualities in Iraq resulted in no actual taken against the individual responsible.