Motorists with three or more cases are convicted in 38 percent of cases, compared to 53 percent for all defendants, the Tucson Citizen found in a computer analysis of DUI charges filed in Pima County Consolidated Justice Court from 1990 to June 2005 and in Tucson City Court from 1999 to June.

Some drivers repeatedly charged with DUI have learned how to beat the criminal justice system: They know the loopholes that allow them to provide as little evidence as possible, weakening the case against them.

Nearly 20 percent of them simply don't show up for court dates, knowing they likely won't be arrested as a no-show.

The ability of hard-core drinking drivers to elude conviction has become a vexing problem for the justice system in Tucson and elsewhere. Failure to convict is a huge problem with such drivers because they tend to drink more often and in larger quantities than social drinkers, making them a greater risk on the road, studies have shown.

Consider Juan Alex Valenzuela. Facing two warrants for prior DUI charges, and without a valid drivers license, Valenzuela was driving with a blood-alcohol level nearly twice the current legal limit of 0.08 percent when he crashed into a motorcycle in 1999.

Thomas Barber was nearly killed. Once a participant in judo competitions and bicycle races, Barber had to learn how to walk again. He has brain damage and can rarely say more than a word at a time.

His father, Wally, had retired as a suburban Chicago police officer because of injuries from drunken drivers. He has metal hips that make walking difficult. Since the crash, Wally and his wife have had the full-time job of taking care of Thomas, 48.

Previously a civilian employee for the Arizona Air National Guard, Thomas won't be eligible for retirement benefits for 12 years, which makes his father worry about future care.

"I've got to live at least 12 more years so I can take care of him," said the father, 73.

Last year, seven motorists who had at least two prior DUI cases were charged in alleged drunken driving accidents that caused injuries in Tucson, records show. All seven have escaped conviction at least as many times as they've been convicted.

Between 1999 and the end of last year, 1,033 motorists had three or more DUI cases filed against them. Of those, 40 percent were convicted more than once and can be considered repeat offenders; 263 motorists were charged with DUI at least three times and never convicted.

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