High overtime costs, a hot issue in the race for Dallas County sheriff, became an equally heated issue at the weekly Commissioners Court meeting Tuesday morning.

Commissioner Kenneth Mayfield had asked Sheriff Lupe Valdez to explain her agency’s overtime situation. After the sheriff’s brief presentation, Mr. Mayfield grilled her about why overtime costs have not decreased despite the addition of 400 jail guard positions.

That led to a spirited exchange between the Republican commissioner and Sheriff Valdez, a Democrat, who for the first time during her rare appearances in the court shot back with some zingers of her own.

Sheriff Valdez, who is running for re-election, has won over most of the commissioners - at least publicly - during the past three years. But Mr. Mayfield has remained a vocal and persistent critic of her policies.

Sheriff Valdez told the court that overtime is down. But county auditor’s records show that her department has spent more than $18 million on jail overtime alone during the past two years - the highest in recent memory.

The sheriff has had to fight for every budget request. Although she hasn’t got what she’s asked for since taking office in 2005, new positions have been added here and there throughout the years as needed.

“If we can get the people we need, it’s easy to meet our goals,” Sheriff Valdez told the commissioners as her command staff and campaign manager watched from the wings.

Mr. Mayfield, his voice rising in anger, told the sheriff the court is used to getting copies of presentations beforehand.

Sheriff Valdez said it wasn’t completed until that morning and asked whether other county departments are held to that same standard.

Mr. Mayfield told her it appeared that every time the court added more guard positions, sheriff’s overtime “seems to increase.”

Commissioner John Wiley Price, a Democrat, jumped to the sheriff’s defense, saying the month-long academy classes can accommodate only 40 recruits at a time. Mr. Price, who has voluntarily overseen many jail improvements, also said the department has been hampered by turnover when jail guards apply to become deputies.

Sheriff Valdez, who has in the past politely defended her actions, did not hold back this time.

“I know you don’t want to put another penny into the jail,” she told Mr. Mayfield.

That attitude, she added, is “what got us in trouble” in the first place.

A little later, when Mr. Mayfield asked for some information, Sheriff Valdez replied with a smile that she had just showed it during her presentation. “I don’t know if you were paying attention,” she said, shaking her head.

At the end of the heated discussion, Mr. Mayfield demanded to see a breakdown of numbers that clearly show how new positions have affected overtime in each of the various jail departments.

Ryan Brown, the county’s budget director, said he will meet with sheriff’s officials to work on the numbers and provide them to commissioners as soon as possible.