Science and our legal system intersect frequently and everywhere - climate, health care, intellectual property, you name it. It wouldn't make much sense to hire an environmental lawyer for a case on medical malpractice, but what about the judge overseeing the case? Should judges be experts in these particular scientific fields?

No, says the Federal Judicial Center and National Research Council, but they should at least be informed and hire experts where needed. The groups recently published the third edition of the Reference Manual on Scientific Evidence, created to assist "judges in managing cases involving complex scientific and technical evidence by describing the basic tenets of key scientific fields from which legal evidence is typically derived and by providing examples of cases in which that evidence has been used."

In the introduction, Associate Supreme Court Justice Stephen Breyer writes: 
In this age of science, science should expect to find a warm welcome, perhaps a permanent home, in our courtrooms. The reason is a simple one. The legal disputes before us increasingly involve the principles and tools of science. Proper resolution of those disputes matters not just to the litigants, but also to the general public – those who live in our technologically complex society and whom the law must serve. Our decisions should reflect a proper scientific and technical understanding so that the law can respond to the needs of the public.
Judges need more than just a statistics formula to do their job, Breyer says; they need to develop an informed understanding of the science.
But science is far more than tools, such as statistics. And that “more” increasingly enters directly into the courtroom. The Supreme Court, for example, has recently decided cases involving basic questions of human liberty, the resolution of which demanded an understanding of scientific matters. Recently we were asked to decide whether a state’s method of administering a lethal injection to condemned inmates constituted cruel and usual punishment in vilation of the Eighth Amendment. And in 1997, we were asked to decide whether the Constitution protects a right to physician-assisted suicide. Underlying the legal questions in these cases were medical questions: What effect does a certain combination of drugs, administered in certain doses, have on the human body, and to what extent can medical technology reduce or eliminate the risk of dying in severe pain? The medical questions did not determine the answer to the legal questions, but to do our legal job properly, we needed to develop an informed – although necessarily approximate – understanding of the science.
Breyer also acknowledges, though, that the variety of cases brought before a judge necessitates that the judges are not experts, but rather that they rely on sound scientific knowledge:
Even this more modest objective is sometimes difficult to achieve in practice. The most obvious reason is that most judges lack the scientific training that might facilitate the evaluation of scientific claims or the evaluation of expert witnesses who make such claims. Judges typically are generalists, dealing with cases that can vary widely in subject matter. Our primary objective is usually process-related: seeing that a decision is reached fairly and in a timely way. And the decision in a court of law typically (thought not always) focuses on a particular event and specific individualized evidence.
The search is not for scientific precision. We cannot hope to investigate all the subtleties that characterize good scientific work. A jusge is not a scientist, and a courtroom is not a scientific laboratory. But consider the remark made by the physicist Wolfgang Paul. After a colleague asked whether a certain scientific paper was wrong, Pauli  replied, “That paper isn’t even good enough to be wrong!” Our objective is to avoid legal decisions that reflect the paper’s so-called science. The law must seek decisions that fall within the boundaries of scientifically sound knowledge. 
For my money, the most interesting paragraph touches on the difference between scientific process and the legal process. The law, Breyer says, is about a fair and due process:
Finally, a court proceeding, such as a trial, is not simply a search for dispassionate truth. The law must be fair. In our country, it must always seek to protect basic human liberties. One important procedural safeguard, guaranteed by our Constitution’s Seventh Amendment, is the right to a trial by jury. A number of innovative techniques have been developed to strengthen the ability of juries to consider difficult evidence. Any effort to bring better science into the courtroom must respect the jury’s constitutionally specified role – even if doing so means that, from a scientific perspective, an incorrect result is sometimes produced.
Essentially, scientists and legal experts should work together to inform each other to better serve the general public. For tangentially related reading, Hank has an interesting piece about climate tribunals here, and Patrick discusses the laws of nature and natural justice here.

Tip o' the hat to the huz and Slashdot.