Kuah K.L*, Michael Tay Ming Kiong
2nd International Forensic Science Symposium, Taipei, Taiwan. November 2005. (poster presentation)
Purpose of Research
Lightning is fascinating to watch but is also extremely dangerous. A cloud-to-ground lightning discharge can extend to over 8 km in length, reach a temperature of over 27,000oC, a direct current of over 200,000 amperes and a voltage of over 30 million volts. Despite the high temperatures, voltages and currents generated, a lightning strike typically has a very short duration of 1-2 milliseconds.
Lying almost on the Equator, Singapore has one of the highest lightning rates in the world, with an average of 171 thunderstorm days a year. The most frequent occurrence of thunderstorms in Singapore is between 2 and 6 o’clock in the afternoon. The case involved a tall 18-year-old male soccer player, who was struck and killed by lightning during a training session in a football stadium at about 4 pm on March 10, 2004. Before the incident, eye-witnesses recounted a light drizzle with dark skies but no thunder or lightning. The football coach, who was standing near the victim on the open pitch said he suddenly heard the roar of thunder and then saw a lightning bolt hit the ground behind him. The victim immediately collapsed onto the ground with smoke rising from his left foot. He was pronounced dead at the scene by rescue workers about 10 minutes later.
Problems to be solved
This paper presents findings on damages on clothing items and shoes worn by a victim during a fatal lightning strike. The aim of this case study was to identify damages on clothings that are characteristic of a lightning strike, as opposed to cuts, tears, and normal wear and tear. These observations can be useful in coronial inquiries in supporting a direct lightning strike as the cause of death in cases where witnesses are not available or when the bodies are not recovered in time for significant autopsy findings.
The jersey, shorts, socks and spiked shoes worn by the victim at the time of the incident were submitted to our laboratory for examination of damages. The damages were examined macroscopically and microscopically. Two metal pins were found on the sole of each shoe, near their front tips. In order to reveal possible damages on the inner sole of each shoe near the metallic pins, the shoe uppers were slit open just above the soles at the front and pulled backwards.
Results and Discussion
Numerous tiny holes were found on the victim’s jersey and shorts. A circular hole, measuring approximately 0.4 cm in diameter, was found on the jersey. Slight blackening was observed at the edges around the hole with some melting of the thread ends. More similar tiny holes were found on both sides of the shorts. On the front right side of the shorts, under the waistband, was a circular hole measuring 0.3 cm in diameter. At the back of the shorts, a cluster of six tiny holes of about 0.1 cm size was found in the lower left region. The holes all had similar characteristics of blackening and melting around the edges.
Large holes were found on the victim’s socks and shoes. A large hole measuring approximately 1 cm in size was found at the side of each sock at the position of the large toe. Melted materials from the shoe lining were adhering to the edges of the holes. These holes corresponded in location to the holes observed on the inner soles of the shoes, situated above the metal pins on the front tips of the soles.
This case study described damages caused by lightning currents travelling in a vertical pathway through the body of a perspiring victim and out through his clothes and shoes to ground. Passage of the currents resulted in small holes in the garments, socks and shoes with characteristic melting and charring around the edges of these holes. The melting and charring observed indicated intense heat for short durations at these localised spots. The parts of the socks and shoes that were most damaged were at the metal pins which formed a preferred conducting pathway for the lightning currents to the ground.