Congress and the Courts have influenced the selection process by placing the burden of proof on the employer to show that any given selection requirement, including the interview, must have a specific relationship to the job in question.  

In several landmark cases, the Courts ruled that "the cornerstone in the construction of a content valid examination is the job analysis" (Kirkland v. New York State Department of Correctional Services) and  "job relatedness cannot be proven through vague and unsubstantiated hearsay" (Albermarle Paper Company v. Moody).  

One of the most important court cases involving job analysis was Griggs v. Duke Power. This case outlined the need for conducting an analysis of the job for which a selection procedure has been developed. In this case, the court emphasized that a selection tool should measure the person for the job. In other words, hiring employees because they seem like a hard-worker, they have a good personality, or they go to your church isn't enough. What matters is can they do the job? 

Commenting in this case on Title VII of the the 1964 Civil Rights Act, the court stated:

• Nothing in the Act precludes the use of testing or measuring procedures; obviously they are useful. What Congress has forbidden is giving these devices and mechanisms controlling force unless they are demonstrably a reasonable measure of job performance...What Congress has commanded is that any tests used must measure the person for the job and not the person in the abstract

In Kirkland v. New York State Department of Correctional Services, the Court noted that the State was not able to show the job relatedness of a selection test. The Court noted that there was no adequate job analysis.  

Neither Congress nor the Courts has said that tests are illegal. They just say that any tests, inventories, or procedures used for selection must test for job-specific and job-related skills or traits. Selection activities include internal promotions and succession as well as bringing new employees from the outside. And as you can see from the list below (source: An Employer's Guide to Good Practice, U.S. Department of Labor), personality tests are no more illegal to use in selecting the best employees for a job than the interview.  

The issue of legal or illegal is based on job relatedness. The Uniform Guidelines on Employee Selection Procedures states that a thorough job analysis is needed for supporting a selection procedure. As a result the job analysis can be the proof an organization needs to defend its use of tools and techniques that screen out mis-matched, unskilled, or disruptive employees and select in the very best people for the job.