If you need an expert witness in a case, you can ask the law firm you have retained to locate one, or you can use one of the many services that specialize in finding experts (See my post of Feb. 2, 2008: expert witnesses with 9 references.).
When outside counsel locate the expert and conduct vetting phone calls., law departments typically pay for their help at an hourly rate. Boutique services are out there, however, that do not charge by the hour, let alone the hundreds of dollars an hour and lots of hours a law firm might charge. A principal of IMS ExpertServices makes this point in the In-House Defense Qtrly., Summer 2011 at 6 (See my post of Feb. 13, 2008: Round Table Group and its 95,000 experts; and Nov. 1, 2010: allow non-lawyers to assist with expert witness preparation.).
I can hear the objections already: the law firm will duplicate much of the work anyway. And, if anything goes other than as hoped with the expert’s role in the case, fingers will point.