This week, we bring you a two-part series from Tyler K. Wilkinson examines how social media, especially Facebook, has blurred the lines between personal and professional life. In this post he addresses the question “Should employers friend a job applicant on Facebook?”

Screening job applicants online has become increasingly popular and easy to do. A recent report reveals that almost half of companies surveyed use social media sites to scope out potential employees before making a hiring decision. And job applicants increasingly are using social media sites to distinguish themselves from competitive applicant pools. Why? Social media sites can provide a wealth of information about an applicant that’s not typically included in a resumé.

But refusing to hire a job applicant because of information discovered from online screening may be against the law. Title VII of the Civil Rights Act of1964 prohibits you from refusing to hire an applicant because of his race, color, religion, sex, or national origin. Many state laws go even further, prohibiting you from refusing to hire an applicant because of  things like ancestry, arrest or conviction record, marital status, pregnancy, sexual orientation, genetic information or use or nonuse of lawful products outside of work, among other things. Additional statutes prohibit you from refusing to hire applicants because of age, disability, and military service.

So what’s the problem with using social media to screen applicants?

Many times, the information an individual posts includes protected characteristics. It’s not hard to imagine a Facebook profile page in which an applicant indicates he is gay or a Twitter announcement by a job candidate that she is pregnant. You could decide not to hire a job applicant after seeing that he “likes” a particular alcoholic beverage’s website. When justifying why a particular applicant wasn’t hired, it can be hard to segregate illegal reasons from legitimate ones. As one commenter put it, “you can’t unring the bell.”

Technology for HR and HR Laws subscribers’ tip: Research social media policies and what you should tell employees about social media online.

Your decision not to hire a particular applicant based on information you found online can expose you to liability. Although refusal-to-hire claims are difficult to prove, online searches leave a trail and often can be used as evidence in civil litigation.

In one major refusal-to-hire case, a leading candidate for a teaching position at the University of Kentucky was knocked out of the running after someone at the school performed an Internet search and turned up evidence of his extreme evangelical beliefs. The university informed the applicant of the Internet search and of its concern with his views. The school hired someone else, and the dejected candidate sued. The case settled for $125,000. Refusal-to-hire claims may become more prevalent as more companies decide to screen applicants online. Gaskell v. University of Kentucky.

To protect your company from liability, keep these pointers in mind:

If you intend to conduct an Internet search of a job applicant, tell him so in the interview. Telling an applicant that you plan to “google” his name gives him notice as well as an opportunity to clean up his online presence.

• When screening job applicants online, limit your searches to aspects that are legally defensible ― e.g., bona fide occupational qualifications, job-specific education, relevant skills, and experience.

• Consider hiring an internal screener or third party to monitor and document applicants’ social media posts. A designated employee or third party can forward relevant (and legal) information to individuals possessing the authority to hire employees. That will prevent potential refusal-to-hire charges.

Tyler Wilkinson is a third-year law student at the University of Wisconsin Law School.   Prior to law school, he taught special education students in New York City through Teach For America.  Tyler was a summer associate at Axley Brynelson, LLP in 2011.

The Technology for HR manual shows you how to harness the power of social media for the good of HR while keeping employees from crossing any illegal lines.