Disaster Film . . . If a picture is worth a thousand words, a videotape can be worth $22 million. At least it was to the lawyers at Eckert Seamans Cherin & Mellott, who used a nine-minute video documentary to persuade the National Transportation and Safety Board to reverse its ruling on what caused a 1996 fire on a Federal Express DC-10. Investigators had focused their scrutiny on a DNA synthesizer on board as the potential cause of the fire, which left the synthesizer’s manufacturer -- Eckert Seaman’s client PerSecptive Biosystems -- vulnerable to a suit by Federal Express for the loss of the aircraft and its cargo. “There was a lot of documentation here about how the fire happened, and it was awfully difficult to follow on paper,” says Jerry Cox, a partner in the D.C. office of Eckert Seamans. So Cox hired the McLean, VA., television production firm Hamilton Productions Inc. to produce a $40,000 video documentary of what Cox says is evidence that the fire broke out some 30 feet away from the DNA synthesizer. The NTSB now considers the fire of undetermined origin.