Daniel Andrade, a former Sacramento City Unified School District custodian, hurt his left heel when a cart rolled onto it at work.

For several months he told doctors the pain was so severe it rendered him "inactive," according to court documents.

Yet on various occasions, private investigators filmed him during hours of yard work, even loading a lawn mower onto his truck. He moved about freely and did not appear to be in pain.

Earlier this year, the footage helped convict Andrade and send him to jail for a year.

He also was ordered to pay $250,000 for defrauding his employer.

Andrade's conviction marked another victory, among more than 20 statewide in two years, for Probe Information Services, a Citrus Heights firm that investigates workers' compensation fraud.

Since 2006, the company has investigated 20 percent more cases of fraud, said Dalene Bartholomew, who heads Probe's special investigations unit.

Workers' compensation payments – which are tax-free – are often higher than unemployment payments, fraud investigators said. And with the economy sliding and unemployment on the rise, Bartholomew and law enforcement officials said they expect to see more cases.

Just in the past year, 30 percent more suspicious claims have landed on her desk, Bartholomew said.

In California, potential losses to workers' compensation fraud ran about $223 million in the 2006-2007 fiscal year, according to the state Department of Insurance.

"The economic situation is kind of bleak," said Sudha Rajender, a San Joaquin County deputy district attorney who noted a 25 percent increase in his office's caseload. "Many people are out of work, so they get creative with raising funds."

Since most county district attorneys give priority to violent crime cases, employers have turned to companies like Probe to build stronger workers' comp cases and improve chances of prosecution.

"We want to take care of employees who have been hurt," said Dale Carlsen, president of Sleep Train Mattress Centers. "Unfortunately, there are some (who are) less honest about it and cheat the system."

Carlsen said fraudulent claims drive up insurance premiums and leave less money for those who are truly in need.

Probe has helped Sleep Train save tens of thousands of dollars, Carlsen said.

In the past two years, Probe investigations have led to 25 arrests and of those, 21 convictions, Bartholomew said.

In one case, Probe's evidence prompted Santa Clara County investigators to look at a Palo Alto city employee who was receiving workers' comp benefits for a back injury. The employee was caught building garage cabinets, Bartholomew said.

Probe has succeeded because its investigators understand the criminal justice system and know what evidence is needed, said Rajender, the San Joaquin County deputy district attorney.

"When they present a case it is well-organized, as opposed to dumping a 6-inch stack of documents on my desk," Rajender said. "If it is organized, it is much easier to review and mark the key documents for evidence."

Prosecutors often rely on companies like Probe to do field work, said Chris Champlin, an investigator at Probe and a former police officer.

Probe, with about 60 employees, plans to hire 15 more investigators and extend operations to cover much of the western United States.

Many of Probe's cases come from self- insured employers who don't have traditional insurance company fraud units to rely on, Bartholomew said.

Bartholomew said investigators watch workers' comp fraud suspects for long stretches, following them into malls with hidden cameras and disguises. If someone goes camping, investigators also go camping, she said.

Probe's Lindsay Roberts watches hours of tapes to process evidence.

"I see people moving boxes and doing a whole bunch of stuff they shouldn't," Roberts said.

She said she's seen cases where a person uses crutches the whole day, but then leaves them in a car and walks on a supposedly injured foot. Those are the moments, she said, when she exclaims: "Oh, you're nailed!"

Call The Bee's Chelsea Phua, (916) 321-1132.