One of the unexpected consequences of the increased diligence of national security agencies in the wake of the 9/11 attacks was the large number of baseball players whose visa documents were found to be fraudulent. Latin American players, it turned out, had been falsifying their ages, claiming that they were younger than was actually the case.

This did not come as a shock to anybody in the sport; it had long been known that Latin American prospects often lied about their age, and occasionally the truth about a specific player would come out. But the breadth of falsification was staggering: More than 300 major and minor league players were fingered as frauds.

The federal investigations turned up some big names, such as Miguel Tejada, and they spurred Major League Baseball to come up with a solution to the problem of age falsification: DNA testing. For the past several years, major league teams have been performing DNA tests as well as bone scans to ascertain the true age of international prospects. The prospects must pay for the tests themselves, and if the tests confirm their age and identity, they get reimbursed.

Before the tests, prospects could get away with presenting other peoples’ birth records as their own. A DNA test cannot determine the prospect’s age, but it can determine whether the parents he claims are actually related to him.

The problem of players lying about their ages has grown as the number of Latin American players in the major leagues has exploded. Prior to World War II, the number of major league players of Latin American origin was minimal, in part due to segregation, though that was far from the only factor. By 2008, 1 in 5.06 players making their debut in the major leagues was from Latin America.

It’s easy to see, then, why major league teams have such a huge incentive to ascertain their prospects’ ages. Even a couple of years can make a big difference in a player’s development: An 18-year-old holding his own in A-ball is impressive; a 20-year-old not nearly so.

Many prospects take more than a couple of years off their true birthdays. The Washington Nationals, for example, gave 19-year-old shortstop Esmailyn Gonzalez a $1.4 million bonus only to find out that he was actually 23-year-old Carlos David Alvarez Lugo. Baseball America magazine, which tracks prospects, downgraded Gonzalez from the #10 Nationals prospect to outside the top 30.

DNA testing could help avoid such embarrassments, but it may not be around for long—the Genetic Information Nondiscrimination Act (GINA) (PDF), which goes into effect November 21, bans US employers from asking an employee, potential employee, or family member of an employee for a DNA sample. The law applies regardless of a person’s citizenship status.

GINA satisfies privacy advocates who worry that employers may discriminate against employees based on their DNA, but it will probably mean a lot of baseball clubhouse birthday cakes with the wrong number of candles.