First, using pre-employment tests that are reliable, job-related, and valid actually protects you from legal exposure related to hiring by adding an objective factor to the hiring decision.
Kate Williams, a doctoral candidate at Clemson University published a paper: Legal Risk in Selection: An analysis of processes and tools, that analyzed the nature and outcome of legal proceedings involving the EEOC and OFCCP, including all cases related to external hiring (not promotions) that were settled both in and out of court during the time period between 1998 and 2010. The findings reported cover two key areas:
Issues with a particular type of selection measure or test including: unstructured interviews, structured interviews, biodata measures, cognitive ability tests, psychomotor tests, and “other tests.”
Issues with the way the selection tools were used within the hiring process, including the following key issues: lack of documentation, inconsistent process, quota for affirmative action programs, recruiting source violations, violations of the 4/5th rule, and “other” process issues.
A total of 224 complaints were identified. Note that when examined over the 12 years covered by the study, the total of 224 cases breaks out to about 19 per year. The total number of cases that end up facing legal challenges is a very minute percentage when one considers the massive number of hires made each year in the U.S. Additionally, out of these 224 cases, only 52 cases were related to a hiring test, with the rest related to hiring process issues. This works out to be an average of less than 5 cases per year related to a hiring test. Given that employers administer millions of hiring tests per year, you can see how a small percent of these administered tests even end up with a legal challenge.