The high-stakes battle over whether Houston lawyer Ronald D. Krist should help defend BP from suits filed over a deadly explosion at the company’s Texas City, Texas, refinery took another twist on Aug. 20 when a former client who had hired Krist’s firm to sue BP over the explosion filed a professional negligence suit against Krist, the firm and others.

Jose L. Elizondo, who filed Jose L. Elizondo v. Ronald D. Krist, et al. in Texas state court in Harris County on Aug. 20, is one of four individuals who hired the Krist Law Firm to seek damages from BP for the 2005 explosion, which killed 15 people and caused injuries and property damage.