Supreme Court Chief Justice John Roberts says he will no longer participate in deciding a patent infringement case because he discovered he owns shares in the parent company of one of the parties. Roberts took part in arguments in the dispute between California-based Life Technologies Corp. and Wisconsin-based Promega Corp. on Dec. 6. A letter Wednesday from court clerk Scott Harris says Roberts has learned Life Technologies is owned by Massachusetts-based Thermo Fisher Scientific Inc., and Roberts owns shares valued at about $175,000.