A few months later, Will's parents became concerned when their toddler changed. He stopped talking. He didn't make eye contact, smile or wave good-bye. Doctors said he no longer was developing normally, but couldn't explain why.

Lyn Redwood began her own investigation and found a frightening fact. Her son had been exposed to high levels of mercury - a heavy metal know to cause brain damage - as a baby. In fact, Will had received 125 times the allowable limit. The source? Routine shots containing Thimerosal, a mercury-based preservative that was removed from childhood vaccines in 1999.

The Redwoods concluded that mercury poisoning caused their son's illness. They went to court seeking help with medical bills and the cost of caring for someone with autism, which can total millions.

And the Redwoods are not alone. The number of autistic children skyrocketed in the 1990s, statistics show, and many parents and medical experts believe Thimerosal is to blame. Hundreds of lawsuits have been filed against vaccine and Thimerosal makers.

There's evidence that the company that invented Thimerosal, the giant drug maker Eli Lilly, knew its product might be dangerous as early as the 1930s, according to lawyers who represent some of the families. Documents recently uncovered in the pre-trial phase also show that Lilly's own medical department insisted on having "non-toxic" removed from Thimerosal's label in 1967.

But a jury probably never will hear this evidence. The Redwoods and other families are likely never to get their day in court. The reason? The bill creating the new Homeland Security Department, which Congress passed in November 2002.

Although no one disputes that Thimerosal and homeland security are completely unrelated, the bill included a section designed to wipe out all pending Thimerosal lawsuits. The Redwoods were shocked to hear their legal rights had disappeared. They were even more outraged to learn that the section protecting Eli Lilly was mysteriously and secretly added to the bill at the last minute.

"Our children have been silenced by autism and now the votes of Congress have silenced them again," Lyn Redwood said. "It's a sad state of affairs when a pharmaceutical giant is benefitted at the expense of injured children and families whose lives have been shattered by corporate wrongdoing."

Critics of the Lilly provision, including members of Congress from both parties, point out that the drug maker has close ties to Republican leaders in Washington, including President George W. Bush. The company has given millions to congressional campaigns, the vast majority to Republican candidates.

Among other White House connections, President Bush appointed Lilly's chairman to the Homeland Security Advisory Council and a top administration official worked there for 10 years. Lilly has denied being responsible for the provision.

Supporters of the new law point out that it allows families to re-file their cases in a special federal vaccine court. But that's small comfort, lawyers say, because the court provides limited compensation and it's already too late for many families.

The federal vaccine court has a strict deadline for filing cases - three years from when symptoms first appeared. In Will Redwood's case, that was seven years ago.

More information is available at www.safeminds.org, the web site of Safe Minds, a group working to prevent mercury-related injuries. Lyn Redwood is the group's president.