Your question is interesting and one that I encounter quite frequently as law firms continue to expand their Intellectual Property ("IP") practices and Ph.D.'s look for options outside of the lab environment.
People holding doctorates in the biotech, biology, chemistry and the computer sciences areas are in high demand by law firms with strong IP practices. Over the past five to ten years, the biotech field has grown dramatically and, as a result, law firms, and particularly IP boutiques, have developed fairly sophisticated IP practices, successfully filling their ranks with attorneys with undergraduate and graduate degrees in computer science, mechanical engineering, electrical engineering and chemical engineering. Many (but certainly not all) firms have supplemented these practices with technical advisors and patent agents, scientists who typically hold Ph.D.'s but who don't necessarily have law degrees. Sometimes, these advisors/specialists come on board with no legal training. With or without training, these specialists are employed by the firm to assist with the preparation of patent applications. Technical specialists will generally also prepare to take the patent bar exam, which allows them to prosecute patents before the United States Patent and Trademark Office ("USPTO"). Law firms usually require their specialists to take this exam within the first year or two of coming on board.