By definition, the word forensic comes from the Latin word "forensic," meaning "to the forum." The forum was the basis of Roman law and was a place of public discussion and debate pertinent to the law. This meaning has survived to this day, and forensic is still used to refer to matters applicable to the courts. Forensic engineering has been defined as the application of the art and science of engineering to matters at issue in the court system.

By virtue of their formal education, technical experience, ethical standards and professional recognition, engineers are accepted by the courts to give testimony as expert witnesses regarding their opinions, interpretations of test results, and research data. Fact witnesses, on the other hand, are not permitted to give opinions, speculate or testify as to what someone else said, did or wrote. Fact witnesses are allowed to testify only to the facts of which they have first-hand knowledge.

The term forensic engineer was not even in my vocabulary until after I had been doing it for almost a year. During the course of operating commercial and industrial mechanical and general construction companies for more than 20 years, lawsuits had become just another hazard of doing business. Naturally, it had been necessary to testify in court in defense of these lawsuits. Fortunately, we prevailed. Each time, the lawsuits were found to be without merit. Our attorneys said we won because they were good--and that they had a good witness. As a result, I found myself helping them with other construction-related cases. This got me hooked on forensic engineering, eventually to the exclusion of any other engineering practice.

Most forensic investigations are not very exciting. There is no "typical" case. Cases come into the office by telephone, letter, fax, and a few in person. Initially, all the facts surrounding the case have to be gathered and documented. The most important thing is to establish from the beginning what your client expects you to be able to do. If you think you can't do it to their satisfaction, don't take the case. You will preserve your reputation, and probably improve it with your client, if you pass on something that is not completely within your field of expertise.

Forensic engineers usually compile a resume that includes their educational background and professional experience. The legal profession refers to this as a CV, for "curricula vitae." This should be detailed enough to describe your area of expertise to your prospective client. Unfortunately, there are attorneys that do not know what a Professional Engineer is capable of doing. Puzzled looks often appear when a Professional Engineer tries to explain the fields of mechanical, electrical and civil engineering.

Others will try, especially in court, to characterize engineers as only able to operate in very narrow and specialized fields. An example of this could be an engineer experienced in calculating the stresses in boilers being questioned and challenged in court by an opposition attorney as to the engineer's ability to calculate the stress in a piece of pipe. It is not just that they don't get it, it is to make the judge or jury think that we don't get it.

The Plugged Toilet

Forensic Plumbing? Usually it's a dull subject, but not necessarily a dry one. A lot of plumbing cases involve leaks. One very wet case involved a plumbing company that was called to unstop a toilet in a high-rise building, and was being sued for flooding the bottom three floors of the 10-story building. An investigation of the building revealed the following: The plumber removed a back outlet bowl from its carrier on the sixth floor. Finding no apparent blockage, he ran a cable through the carrier, the 4-inch horizontal waste, and down into a 6-inch screwed wrought iron riser. Then it got stuck. He apparently assumed the cable had traveled down the pipe for whatever length he had uncoiled. Actually, it was found that the cable had turned around on itself inside a tucker fitting. The tucker fitting had been used to cut into the 6-inch stack at the fifth floor to install a new toilet room. After it turned around, the cable went up the stack and wrapped around itself at the sixth level. The plumber must have been looking for the cable on the fourth floor, got frustrated, and attempted to cut the 6-inch riser with a portable electric band saw. Then his band saw blade jammed. The blade was still stuck in the pipe. There was a come-along still attached to the pipe just above the cut. The other end of the come-along was attached to an old 2-inch galvanized cold water header in the pipe chase above. It had bent a little, and then it broke.

This started out to be a sewer job, so the plumber hadn't shut any water valves. He summoned the building manager, and informed him that "something" had broken. In the time it took them to find the valves, the three lower floors had standing water. The plumber, I was told, called his boss, left the buildings; and never came back.

The Poltergeist Effect

The case in question concerns a newly constructed school in which "nothing worked." My client was the law firm representing a bonding company for a general contractor that had declared bankruptcy before completing the school. Attending my first meeting with the school board, the engineers, the architects, the contractors and everyone's attorneys, I found each party blaming the other. My comment afterward to my client was that I was the only one at that meeting who hadn't been blamed for something. "You will be," he replied. "Wait until the next meeting."

The school had been accepted for beneficial use, and classes had started in September. The school was located in South Louisiana where the weather seldom gets below freezing until January. That year it happened before the Christmas holidays. The heating system in the school wasn't able to raise the temperature in the buildings above 42K F. As a result, the students were sent home and the school was closed.

Naturally, this got the local news media's attention, and the school board was questioned about it. The board blamed the architect, who blamed the engineer, who blamed the subcontractors. The general contractor had gone bankrupt. The bonding company had to finish construction of the school and used the bankrupt general contractor's subs and the school board's Clerk of the Works. I remembered the founder of our company using the term "Clerk of the Works" to describe inept bureaucrats capable of doing little more than pushing paper. Although I never met the clerk, our founder's description was accurate.

That first meeting was held in the principal's conference room. The weather had warmed to the mid-40s and the temperature in the conference room was cool, but not uncomfortable. Before the meeting started, something strange happened. About every five minutes or so, the temperature in the room would drop suddenly. There was no apparent sensation of any air movement. It just got cold. Through all of this, the supply grills were still delivering warm air. The temperature appeared to drop almost instantly. Within a few minutes, the temperature would increase and the chill would be gone. It was like something from the movie "Poltergeist." As the conference room filled with more warm bodies and the meeting began, the Poltergeist effect was less apparent.

In turn, each of the subcontractors described their work as being completed according to plans and specifications, and that any problem had to be the fault of the other guy. I was taking notes, waiting for the chance to see all this wonderful work.

The principal of the school, who chaired the meeting, explained that the work performed by the bankrupt general contractor was not the only work that was unacceptable. It was explained that an inspection of the heating system would be made for those present for the HVAC problems. However, we would have to wait. There were other contractors that had been awarded separate contracts by the school board that also needed to be addressed.

The architects' mechanical engineer had specified a self-contained energy management system (EMS) that was to be installed on the premises. The supplier of the system, the temperature control subcontractor, had submitted a proposal to the school board offering to furnish a more elaborate system at no additional cost above the original bid. The proposed system had the capability, with future additional costs, to control all of the district's schools from a central computer. The school board accepted the proposal and issued a contract for the revised EMS system directly to the temperature control subcontractor. It was not handled as a change order to the general contractor, and through the mechanical contractor for whom the work of the temperature control subcontractor was being administered. In doing this, the school board saved two tiers of mark-up. But they lost the control over the work that is normally afforded through change orders.

Neither the mechanical or the general contractor could be held responsible for the proposed system, as it was not part of their contract. Nor could the architect or engineer be held accountable, as it was not their design. The mechanical contractor made it perfectly clear at the meeting. He was not responsible for the EMS and blamed all the problems with the school on the EMS. By this time, the proceedings were getting more complicated than a good murder mystery. Everything that could go wrong with a construction project seemed to have gone wrong with this one. The meeting recessed so that the school board could inspect the library's new computer system, which also was not working to the principal's expectations. Left in the conference room with only my client, the poltergeist effect was again apparent.

The supply and return duct work had to be installed above the lift-out ceiling. The supply system appeared to be delivering a steady supply of warm air. How could the return air system be responsible for such a chilling? Opportunity and curiosity won out over better judgment. I arranged four legal pads on the conference table and placed the legs of the biggest chair in the room on top of them. The attorney said something, but I wasn't really listening. It had something to do with being either focused or obsessed. The tallest chair in the room was then placed on top of the chair already on the table. Carefully ascending to the top of the makeshift scaffold, I removed one of the ceiling panels and poked my head into the space above the ceiling.

Once above the lift-out ceiling, the mystery was solved. There was no ceiling above the lift-out. The return air was open to a ventilated attic. Anytime an outside door was opened, heated air flowed into the open attic area. It was quickly replaced by colder air, which dropped down into the room below. I climbed down with such a big grin on my face that the attorney quit talking in mid-sentence. "I found it," I said.

In puzzled disbelief, he said something like, "You mean that you found in less than three minutes what the design engineer and architect could not find in the last three months?"

We unrolled the set of plans on the conference room table. The architect's drawings of the wall sections at the conference room showed a single horizontal line above the lift-out ceiling. Nowhere on the plans was this single horizontal line identified as a ceiling or as a required return air plenum. The single line coincided with the height of the top walls of the conference room. Nowhere on the mechanical plans was there any return air duct work. It had apparently been "assumed" by the mechanical engineer that the architect had indicated there was to be a plenum ceiling there.

With no indication on the plans that this single line represented anything more than the top of a wall, the sheetrock subcontractor did not install the ceiling. Nor did the mechanical contractor question the absence of the necessary plenum. To top it off, the general contractor wrote no letters to the architect regarding clarification. The Clerk of the Works didn't catch it and had authorized full payment to all of the subcontractors. When confronted later, the architect argued that this line meant there was to be a ceiling.

In cases such as this one, you learn quickly that the human tendency toward pre-judgement is one of your worst companions. As initially presented, a case may seem bogus. "It could not have happened that way," you may think. However, the error is usually in the assumption, or the visualization of what you perceive to be "that way." In reality, it may not have happened "that way" at all.

The Exploding Air Conditioning System

A good example of this was an "exploding air conditioning system" that I investigated. As presented, a reportedly experienced air conditioning repairman sustained serious burns when a refrigeration system exploded when he was checking it for leaks. Having never seen a refrigerant system explode, my first thought was that this was going to be another bogus claim. My next thought was, "What kind of explosive gas did the repairman use to do the leak test?" Propane? Butane?

Upon examination of the system, the compressor body had split open, the condenser tubes had ruptured, and the return bends blown off the evaporator. There was no doubt there had been an explosion and the explosion had occurred on the inside of the refrigerant circuit. An examination of the testing equipment that he used to do his leak testing showed he had used high pressure oxygen. He had removed the high pressure gauge from the regulator on the oxygen cylinder of an oxy-acetylene rig, made an adapter, and connected his set of refrigerant gauges through the adapter. The refrigerant hoses were blown apart. The refrigerant gauges were beyond pegged. The gauge needle had hit the pin, deformed around it, jumped the pin and appeared to have made another revolution.

Did the repairman think he was using the most environmentally friendly stuff around? Maybe so. My father was a welder and taught me that oxygen and oil spontaneously explode. Oxygen gauges, including the one this repairman was using, have written on their faces "Use No Oil." I thought every welder, pipe fitter, plumber, and refrigeration technician would have been taught this. Obviously, this one had not.

Although I was asked to write about forensic plumbing, I chose to include stories about heating and cooling cases as well. The lessons are there for engineers involved in any segment of the industry. We all learn from our own mistakes. Forensic engineers analyze the mistakes of others, and hopefully we all can learn from them too.