Twelve people died and at least 87 others were sickened by the outbreak of a disease in Flint, Michigan during 2014 and 2015. Many doctors diagnosed their patients with Legionnaire’s disease, a noncontagious condition with symptoms similar to pneumonia.

Legionnaire’s disease is caused by bacteria that live in water. Most people acquire the disease by inhaling water droplets that contain the bacteria. Some experts are attributing the disease outbreak in Flint to the city’s water supply. Other experts disagree.

Criminal prosecutions are underway against state officials responsible for municipal water quality. Prosecutors allege that the officials failed to alert the public about a Legionnaires’ outbreak in Flint and that they conducted a grossly negligent investigation of the outbreak.

Expert witnesses for both the prosecution and defense are playing a key role in preliminary examinations that are held to determine whether the evidence is sufficiently strong to justify a criminal trial. Additional experts may testify if the cases proceed to trial.

Legionnaire’s Disease in Flint

The outbreak began soon after Flint changed its water source from Lake Huron to the Flint River, a switch that produced discolored and foul-smelling tap water. Scientists concluded that the city’s water supply was contaminated by lead and other heavy metals, but that finding would not necessarily explain an outbreak of Legionnaire’s disease.

Scientists eventually focused on chlorine, which cities often add to water supplies to keep bacteria from reproducing. They discovered that Flint’s chlorine level dropped, and that Legionnaire’s disease increased, after the city changed its water supply.

Lead and heavy metals in the new water supply may have interacted with the chlorine that the city added to the river water, reducing the amount that was available to kill bacteria. The city was also faulted for failing to add corrosion-control chemicals to the water, which may have allowed lead to leach from older pipes. However, other experts contend that chlorine levels do not adequately explain the disease outbreak.

After Flint switched back to its original water source, new reports of Legionnaire’s disease returned to their normal levels. That outcome tended to confirm that the disease outbreak was caused by the new source of Flint’s water.

A report by the Michigan Department of Health and Human Services nevertheless suggests that most of the patients with the disease may have been exposed to it at McLaren Flint Hospital. The hospital responded by accusing the state of using a self-serving and unsound methodology to shift blame from state officials to the hospital.

Criminal Charges Filed

Notwithstanding the confusion about the exact cause of the Legionnaire’s disease in Flint, criminal charges were lodged against more than a dozen state officials, including the state’s Health Director and its chief Medical Officer.

The most significant charges are negligent manslaughter. Two manslaughter charges were filed against Nick Lyon, the director of the Michigan Department of Health and Human Services. Manslaughter charges were also filed against two officials of the Michigan Department of Environmental Quality (DEQ).

The manslaughter charges relate to men in Flint who allegedly died from Legionnaire’s disease. Those officials and others were also charged with willful neglect of duty and misconduct in public office.

Expert Testimony in Manslaughter Prosecution

Lyon sought dismissal of the manslaughter charges during preliminary proceedings. Expert witnesses for the prosecution and for Lyons presented competing opinions about the cause of the victims’ deaths.

Prosecutors used a number of experts to establish that the Legionnaires’ outbreak was caused by the change of Flint’s water supply to the Flint River. Prosecutors contended that the state (in a decision made by Lyon) required Flint to use the new water supply as a cost-saving measure.

The prosecution relied on the testimony of Dr. Joel Kahn, a nationally known cardiologist from Metro Detroit, to establish that the two alleged manslaughter victims died from Legionnaire’s disease. The defense challenged whether Dr. Kahn was qualified to give that testimony since his expertise is in cardiology rather than epidemiology or infectious diseases.

Dr. Jeffrey Band, an epidemiologist and infectious disease specialist at Beaumont Hospital in Royal Oak, testified that the two men did not die from Legionnaires’ disease. He acknowledged that one of the men acquired Legionnaire’s disease but maintained that the disease was treated promptly and effectively. He opined that the man died from an unrelated heart condition.

Dr. Kahn, however, testified that Legionnaire’s disease was the triggering cause of the man’s death. Dr. Kahn also opined that the other man died of Legionnaire’s disease and pneumonia “rather rapidly” after exposure to the disease. Dr. Kahn testified that Legionnaire’s disease was the only cause of that man’s death.

The judge presiding over the preliminary examination recently decided that the evidence was sufficient to permit the case to proceed to trial. Questions about the qualifications of experts are likely to arise again in pretrial Daubert motions. Additional medical experts may be needed to satisfy the prosecution’s burden of proving causation.

Expert Testimony in Misconduct Prosecutions

Proceedings are also underway in criminal charges of misconduct in public office filed against DEQ officials Stephen Busch, Michael Prysby, Patrick Cook, and Shekter Smith. Smith and Cook are also facing manslaughter charges.

The prosecution alleges that the officials neglected their responsibility to oversee Flint’s water source switch and to warn the public about water quality issues. The failure to implement anti-corrosion controls allegedly resulted in high levels of lead that were hidden from the public.

During a preliminary hearing, U.S. Environmental Protection Agency water expert Miguel Del Toral testified that the DEQ knew that Flint was not treating its water with anti-corrosion controls but took no action to assure the safety of the water supply. He also testified that Flint’s water treatment was not meeting federal standards and faulted the state for mandating the change of the city’s water supply without assuring that corrosion controls would be implemented.

Del Toral testified that he found high lead levels in the water in one Flint home after Busch told the homeowner that the problem was caused by her lead pipes, not by the city’s water supply. Del Toral discovered that the home had plastic pipes and could not have contributed to lead contamination. According to Del Toral, Busch’s response was misleading and underplayed the significance of the problem.

The preliminary hearing against the four defendants is scheduled to resume in September.