The results of their probe may change the way people with special needs are evacuated and the way commercial buses are regulated.
Maples, wearing a dark suit, arrived in the courtroom Monday morning and sat quietly with family members while potential jurors gathered in an adjacent room.
The conspiracy charge, the most serious in the three-count indictment, carries up to five years in prison and a $250,000 fine. If the company is convicted on that charge, it could be fined $500,000.
The accident is believed to have been caused by an overheated bearing in the rear wheel well, probably the result of poor maintenance. The tire ignited and the fire engulfed the bus, then probably caused oxygen canisters to explode, investigators said.
The bus had been on the road 13 hours in heavy traffic, fleeing Hurricane Rita, reports L.P. Phillips of CBS Radio station KRLD. Motorists had tried to warn the driver, an illegal alien who did not speak English well, that the wheel hub was so hot it was glowing red minutes before the fire.
Thirty-seven nursing home residents were on the bus. Many were disabled and unable to escape.
Since then, the U.S. Department of Transportation issued new guidelines for carrying medical oxygen, recommending that tanks be secured in an upright position and limited to one canister per patient in the passenger compartment.
The National Transportation Safety Board held a two-day hearing in August to examine state and federal oversight of motor coach companies.
Global Limo was shut down two weeks after the accident.
In May, victims reached an $11 million settlement with Global and with BusBank, the travel broker that hired the bus.
Prosecutors have said the trial will focus on the company's management leading up to the accident.
The conspiracy charge in the indictment alleges that drivers operated in pairs, with one driving and the other resting in the passenger seat. There was no sleeper berth for the resting driver as required by law and indicated in driver logs.
Drivers were allegedly directed to falsely record their passenger-seat time as "off duty" to get around the Federal Motor Carrier Safety Administration's rules for maximum consecutive driving time.
"Those actions resulted in Global Limo bus drivers driving in a tired and fatigued condition, at risk of causing accidents on the nation's highways and elsewhere," the indictment states.
The other charges allege that Maples and his company knowingly and willingly failed to inspect and maintain the buses.
Maples, 67, has been operating tour buses since 1987 and incorporated Global Limo on July 17, 2002. He has spent the last year free on $75,000 bond.
"We're looking forward to presenting the case to the jury and being vindicated of the charges leveled against him," said defense attorney Charles Banker.
The bus driver, Juan Robles, was cleared of charges in exchange for his cooperation. He was directed to stay in Texas as a material witness.
"I'm sure he's grateful that almost a year after the fact this matter is finally going to be resolved," said George Shaffer, a San Antonio-based attorney hired by the Mexican consulate to defend him.