Here are some publicly viewable sources, but not researched and peer-reviewed, which is what I would get for you otherwise:
http://www.aarpmagazine.org/health/health_care_costs.html wrote:
• Malpractice is the culprit Doctors say their worries about lawsuits drive them to order costly tests and procedures that their patients do not actually need. Malpractice reform will help save money, but not as much as some people believe. The Congressional Budget Office estimates that while tort reforms could lower malpractice-insurance premiums for physicians by as much as 25 to 30 percent, the overall savings to our health care system would be a minuscule one-half percent.
http://www.cbo.gov/ftpdocs/49xx/doc4968/01-08-MedicalMalpractice.pdf wrote:
Evidence from the states indicates that premiums for malpractice
insurance are lower when tort liability is restricted
than they would be otherwise. But even large savings
in premiums can have only a small direct impact on
health care spending—private or governmental—because
malpractice costs account for less than 2 percent of that
spending.3
http://online.wsj.com/article/SB125193312967181349.html wrote:
Even so, health-care experts say the direct costs of medical malpractice -- the insurance premiums, claims paid and legal fees -- amount to a very small portion of overall health-care spending.
Total spending on medical malpractice, including legal-defense costs and claims payments, was $30.41 billion in 2007, according to an estimate from consulting firm Towers Perrin. That is a significant figure, but it still amounts to a little more than 1% of total U.S. health-care spending, which the federal government estimates at $2.241 trillion for 2007.
I have other state-specific sources if you'd like.