(April 13, 2016, 1:32 PM EDT) -- OKLAHOMA CITY — A group of plaintiffs who contend that Halliburton Energy Services Inc. (HESI) is liable for personal injuries as a result of the company’s release of radioactive materials into the environment on April 12 filed a brief in Oklahoma federal court, contending that they should be given leave to amend their complaint to add new plaintiffs (Mitchell L. McCormick v. Halliburton Energy Services Inc., No. 11-01272, W.D. Okla.)....