Many amateurs have had success burning lichtenberg fractals into pieces of wood without incident, just as many woodworkers, including myself have used any number of potentially dangerous tools such as table saws, miter saws, circular saws, routers, and dremel tools. Each of those tools can cause massive traumatic injury or death, but by and large, the injuries from these tools are injuries to the hands resulting from momentary carelessness, or inattention. In order to cause fatal injuries, these tools must be used in such a way that an incident causes an injury to the neck or some other artery. Such incidents are much less common.
Contrary to conventional tools, the danger of high voltage burning probes are not isolated to a single, localized spinning blade or tool. Instead, the danger is “catching” in that, the probe is dangerous, but so is potentially any other metal or conductive material that the high voltage comes into contact with. Thus, a mishap with an enegized probe can occur more easily than with a rotating machine. Furthermore, high voltages in contact with a human body have the potential of damaging large portions of the body, and especially the heart. A typical high voltage contact will result in a localized burn at the contact point where the concentrated current enters the body, and potentially a localized burn at the exit point where current leaves the body. The current will naturally perfer to travel through the body through the medium which offers the least electrical resistance. Blood is electrically similar to salt water, and as such will be one of the perferred media. Thus, any high voltage contact incident which involves entrance on one limb, and exit from another, will result in an electrical current passing through the heart, which will cause undesired contractions of the cardiac muscle and can stop the heart temporarily or permanently. Because of this heart seeking, or perhaps heart perferring phenomenon, incidental high voltage injuries are more likely to cause death than incidental spinning blade injuries. In addition to the burns and potential heart injury, the current can also cause unwanted skeletal muscle contractions and failures resulting in flailings and falls that can lead to secondary injuries.
Thus, because of the somewhat incipient (or at least, spreadable) and heart-perferring hazard that can be caused by momentary carelessness or inattention when working with high voltages, additional safety measures are required above and beyond the simple plastic guards used to improve the safety of saws and rotating tools.