(June 6, 2016, 7:04 AM EDT) -- OKLAHOMA CITY — A federal judge in Oklahoma on May 20 ruled that the expert witness for Halliburton Energy Services Inc. (HESI) is permitted to testify in a lawsuit brought by a group of plaintiffs who contend that HESI is liable for personal injuries as a result of the company's release of radioactive materials into the environment and perchlorate into the groundwater (Mitchell L. McCormick v. Halliburton Energy Services Inc., No. 11-01272, W.D. Okla.)....