PIERRE - Nearly a year after state law was changed to require all suspected drunken drivers to submit to blood withdrawals for alcohol-content testing, prosecutors say fewer people are fighting the charges against them.

Legislators debated the issue of mandatory blood tests for years until finally approving them in 2006, making South Dakota just the second state to pass such a law.

Prosecutors used a simple but effective argument in lobbying the Legislature: Driving while intoxicated was the only crime in which some suspects were allowed to withhold evidence.

"The best piece of evidence is the defendant's degree of intoxication, and that's the blood test," said Dave Nelson, Minnehaha County state's attorney.

Nelson and Glenn Brenner, Pennington County state's attorney, say fewer people are contesting drunken driving charges since blood tests became mandatory July 1. They say that has saved money for taxpayers who footed the bills for prosecution, court-appointed defense attorneys and public defenders, and court expenses.

The county is paying for more blood tests, but that's a small price to pay, Brenner says.

"One of the costs you cannot measure is the fact that a lot of these cases do not go to trial anymore," he said. "We're getting a lot more convictions for the crime of driving under the influence. Our streets are going to be much safer when people realize that it's a lot more difficult to get out of a DWI now."

Although the amount of alcohol in a person's bloodstream is the most important evidence in a drunken driving case, earlier state law mandated blood withdrawals only from people who had been arrested for felony DWI. Drunken driving is a misdemeanor until the third conviction.

The 2006 Legislature repealed state law that allowed drivers to refuse blood if they were stopped a first or second time for being drunk. However, those drivers lost their licenses for one year unless they pleaded guilty.

Jurors sometimes were hesitant to convict some people when there were no blood-alcohol measurements, lawmakers were told.

"An awful lot of DWIs that went to trial historically were no-test cases," Nelson said.

Forcing all suspected drunken drivers to provide blood is not without problems. The process sometimes requires several officers when a person refuses to cooperate.

"Some people are combative when they're drunk, but I haven't heard of any unintended consequences," Nelson says. "I know there was some apprehension by jail staff that it might lead to additional problems, but they're just few and far between, and they're certainly not more numerous now because of this change."

The Minnehaha County prosecutor says almost all blood from local drunken driving suspects is drawn at the jail in Sioux Falls. The jail has a contract with a hospital for medical services 20 hours a day, and trained jail personnel do blood withdrawals when hospital staffers are not available, he says.

Under a nationwide standard, drivers with at least 0.08 percent alcohol in their blood are presumed to be intoxicated. That often is referred to as the legal limit, but people can be convicted at lesser blood-alcohol levels if it can be proven they were unable to drive safely.