His life hung in the balance. It was a capital punishment case. He was charged with murder in the first degree and the prosecution had a reliable eyewitness with a seemingly unimpeachable story. Charles Allen testified that he was standing about 150 feet away when William Armstrong , just before the stroke of midnight, bashed in the head of James Preston Metzker with a weight tied to a leather strap.

How could you see who it was when you were at a considerable distance in the middle of the night asked Armstrong's attorney? By the light of the moon said Allen. Are you sure you could see his face? Yes. It wasn't too dark? No, the moonlight was bright. Over and over the young attorney demanded if the witness was certain of what he saw. And the witness was adamant.

It was then that the lawyer produced a copy of the Old Farmers Almanac for the August date in question, and showed the jury that not only was the moon in the first quarter, but was also low on the horizon and about to set, at the precise time of the murder.  The chief prosecution witness had been discredited. "Official" astronomical data proved there was not enough light for Allen to identify Armstrong or anyone.  The jury agreed, and William Armstrong was acquitted.

The young lawyer was Abe Lincoln circa 1857 Illinois. It's a dramatic example of early forensic meteorology.  In the summer of 1985 a commercial jet liner crashed while landing at Dallas-Fort Worth Airport. Investigators working with meteorologists reconstructed the accident and found microburst-induced wind shear from a thunderstorm was a key factor. This lead to aircraft and airport wind shear detection systems and new flight procedures near thunderstorms.

Last month a commuter airline crashed near Buffalo, New York in fog drizzle and snow. Attention quickly turned to the role of icing and ice build up on the plane. Meteorologists will work with investigators to reproduce the weather conditions at all levels of the atmosphere from take off to crash site.

In criminal cases sometimes a defendants story or witness story can be proved a lie or backed up with weather data. Rain or snow add evidence of a time line to footprints or tire tracks backing up or casting doubt on an alibi. Weather conditions impact internal body temperature and body decomposition both used to determine time of death. Archived radar and satellite data have been used to show that a speeding ticket was invalid because the officer indicated too fast for conditions, but the rain occurred elsewhere on the highway not at the point of the citation.

Not all forensic meteorology cases are this weighty. Many involve more mundane weather reports for lawyers and insurance companies involving slips and falls, lightning strikes and hail damage and auto accidents. Sometimes the meteorologist does the research of the data and provides a written report of his findings.  Sometimes the meteorologist will provide a deposition to the court, but will also be sworn in to give expert testimony and be questioned on the stand by the attorneys in the case. Law and Order: meteorology justice. More stories here.