After nearly three years since the largest gas blowout in U.S.history, residents of Porter Ranch still worry whether their health will be compromised five, 10 or 20 years down the road after breathing in not just methane gas, but an array of toxic, often cancer-causing chemicals spewed from an underground gas storage facility in and around their suburban neighborhood.

A key part of their quest is finding out what caused their nosebleeds, headaches, nausea and a few cases of cancer. One answer may lie in the amount of benzene, formaldehyde, arsenic and hydrogen sulfide that accompanied a four-month, uncontrolled natural gas leak from Oct. 23, 2015 until Feb. 2016.

But so far, that information has been hard to come by. Until Wednesday, July 25 when a key witness is expected to testify at a morning hearing on the chemicals released during the natural gas leak.

Break in case

A break came last month during a class-action lawsuit representing about 9,000 residents when attorneys questioned the principal engineer of the chemical and environmental section of the engineering analysis center for SoCalGas about benzene and other air toxics, testing protocols and air monitoring. The testimony — a potential gold mine for the plaintiffs — suddenly dried up when a phalanx of Gas Co. attorneys used multiple strategies to muzzle their employee, thereby preventing May Lew from further testifying.

After months of legal maneuvering, Judge Lisa Hart Cole on Monday ruled against the Gas Co., ordering the witness to testify on Wednesday in a Los Angeles Superior Court courtroom. The exact time and place is still unknown.

The ruling sets up a showdown between the gas company and the residents of Porter Ranch. Her testimony alone could provide evidence of toxic chemical releases, possibly linked to illnesses and negligence. The entire case may hang on Lew’s testimony, which would determine the amount of damages granted residents in the event of a favorable judgment.

“It is a billion dollar answer,” said Rex Parris, lead attorney for the 9,000 plaintiffs, who is also the mayor of Lancaster, a city with a strong environmental mantra. In a case that could reach up to 30,000 claimants, Parris said he’s asking for between $1.5 billion and $2.5 billion. “It depends on whether they settle or go to trial.”

Why is Lew’s testimony important?

There are two reasons why Lew’s testimony may be the most important part of the nearly year-long case.

First, she’s the principal engineer in charge of monitoring what elements are contained in the natural gas that gets pumped into the wells. By listing her responsibilities, it solidified her importance to the case, he said.

“There is not a more important witness,” he said. “Her name appears on 1,700 emails.”

The Gas Co. declined to answer questions about the importance of Lew or her role within the company.

Court documents show Gas Co. attorneys, including Collie James IV of Morgan Lewis, objected 342 times within Lew’s 4.5-hour deposition, something Paris called “an abuse of discovery.” Court records show the Gas Co. attorneys tried to put a time limit on the engineer’s future testimony, said she was too tired to continue and then withdrew her name entirely. In a last-ditch effort, they said she could re-take the witness stand only if the plaintiff’s main attorney, Parris, would be barred from participating.

“The refusal to offer a witness prevents cross-examination on the most critical issue for proving health problems — the toxic chemicals in the gas at Aliso Canyon,” he wrote in a brief from June 5.

Gas Co. attorneys also tried to keep Parris out of the courtroom by accusing him of badgering the witness in an abusive manner, “mocking her for her inability to remember documents,” court records show.

Parris denied the accusations, saying in an interview that the lawyers for the Gas Co. never mentioned this claim until after they tried keeping Lew from the witness stand. “I was very nice to this witness,” he said.

In her ruling, Judge Hart reprimanded the Gas Co., saying the lawyers for the defense must “refrain from coaching the witness or making nuisance objections.” She also denied their request to bar Parris, setting up what many believe will be a fiery but informative exchange that could take days.

“This is the person they designated, the person most qualified to testify on the components of the gas,” he said. “And now, the court says she testifies. He is going to tell me on the 25th what they tested for and why they stopped and why aren’t they testing for it now?”

Second, she’s testified about monitoring for impurities, such as benzene, a very toxic, carcinogenic substance found in gasoline, at first saying there were only “trace” amounts of benzene, then saying the levels ranged from 1 part per million to nine parts per million.

Since the state Office of Environmental Health Hazard Assessment (OEHHA) set the exposure limit at 1 part per billion (with a “b”), the exposure mentioned by Lew would be 9,000 times higher than what the state deemed safe. The state arrived at that reference level in 2014 in order to “protect infants, children and other sensitive subpopulations,” according to the OEHHA website.

During the blowout that left 100,000 metric tons of methane in the air and sent many to the emergency room, Parris said benzene leaked into the air at a rate of 249 parts per million. Long-term effects of benzene can cause cancer by curtailing the amount of red blood cells and bone marrow, which can lead to leukemia. The residents have asked independent doctors to take their blood and evaluate their health. The amount and time of exposure, as well as the individual’s health, are critical factors, according to the Centers for Disease Control and Prevention. In acute exposure, people may vomit, feel dizzy or experience a rapid heart beat.

The Gas Co. released a statement last week, saying the South Coast Air Quality Management District, the OEHHA and the Los Angeles County Department of Health took samples during the leak and months after and found no “long-term risk to public health or safety from the gas leak.

“Furthermore, OEHHA concluded ‘nearly all measured benzene emissions from concentrations in the Porter Ranch community during the leak are similar to background levels generally found in the Los Angeles area,” continued the response.

Was testing done often enough?

Lew initially testified the Gas Co. did not test for benzene or other toxics, such as formaldehyde, according to court records, later saying they did but stopped. One of the line of questions on Wednesday will be about the components of the gas leak?

“Aren’t they obligated to test for what’s leaking into the neighborhood? Their solution to this problem is turning a blind eye to it,” Parris said.