Mississippi had a problem born of the age of soaring student testing and digital technology. High school students taking end-of-year exams were using cell phones to text one another the answers.

So the state called in a company that turns technology against the cheaters: It analyzes answer sheets by computer and flags those with so many of the same questions wrong or right that the chances of random agreement are astronomical. Copying is the almost certain explanation.

Since the company, Caveon Test Security, began working for Mississippi in 2006, cheating has declined about 70 percent, said James Mason, director of the State Department of Education’s Office of Student Assessment.

As tests are increasingly important in education — used to determine graduation, graduate school admission and, the latest, merit pay and tenure for teachers — business has been good for Caveon, a company that uses “data forensics” to catch cheaters, billing itself as the only independent test security outfit in the country.

Its clients have included the College Board, the Law School Admission Council and more than a dozen states and big city school districts, among them Florida, Texas, Atlanta and Washington, D.C.

“Every single year I’ve been in testing there has been more cheating than the year before,” said John Fremer, 71, a Caveon co-founder who was once the chief test developer for the SAT.

Although it is in Caveon’s interest to dramatize or even inflate the incidence of cheating, the company was criticized this year by Georgia’s governor for underestimating it.

Hired to analyze English and math tests from Atlanta students after a state audit identified dozens of schools where cheating might have occurred, Caveon found far fewer problems.

Gov. Sonny Perdue criticized that conclusion and appointed his own investigators in August. In an interview with The Atlanta Journal-Constitution, he accused Caveon of seeking to “confine and constrain the damage” and suggested it was trying to protect its business prospects with other school districts.

Fremer dismissed that suggestion. Caveon’s data forensics on answer sheets were more sophisticated, he said.

Caveon’s philosophy is that it is not necessary to ensnare every cheater to reduce cheating overall. Since cheaters rarely confess, even when confronted with overwhelming evidence, it is better to identify the most egregious cases and ignore the borderline ones.

“Prevention is the goal,” he said, as matter-of-fact as Joe Friday. “Detection is a step. We detect and prevent.”