Burden of Proof

February 25, 2011
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Students practice working with their total stations so that they become familiar with the instrument’s operation and data collecting capability. Such practice is essential for real-life crash or crime scene mapping where time is limited and mapping procedures will be scrutinized in a courtroom.


Surveying and civil engineering firms increasingly are discovering a potentially strong new niche for client work: forensic surveying. Although not new, this market segment is growing, with a constant need for professional surveyors who can apply their experience and skills in applications involving serious accidents or crimes. As one sign that the trend is rising, many state professional surveying associations across the country are now offering special forensic surveying sessions at their annual member conferences.

While the forensic field holds promise for many surveyors, law enforcement professionals trained in criminal investigation methods are finding they also can benefit from learning more about how to properly gather evidence at a crime scene.

Like traditional surveying, forensic surveying involves litigation-related matters. Therefore, in addition to technical expertise, the expert surveyor working in forensic applications also must be knowledgeable about the law, rules of evidence, civil procedure, rules of discovery, property law, tort law, among other legal matters.

A student learns how to set up and begin operating his total station as part of forensic mapping instruction at the Institute of Police Technology and Management in Florida.

There also are varying kinds of forensic surveying. For instance, forensic surveyors may be called upon to gather data at an accident or crime scene or to examine the work of other surveyors to determine whether appropriate methodology and procedure was followed.

Helping drive the attraction of this expanding niche is a wide range of technology for collecting evidence. Although laser scanning has recently been stealing the spotlight, one of the most ubiquitous, yet standard surveying tools--the total station--has experienced its own technological revolution, with newer and faster ways of mapping scenes and collecting evidence at extremely high accuracies.

Thirty years ago, there was little demand for total stations. They just were not available, nor was there other advanced technology that could collect data. The basic steel tape measure was the lone, standard tool for measuring a crash or crime scene.

As total station technology emerged and developed, total station manufacturers reached out to the forensic industry to promote their product as capable of meeting a need for a laser device or a rangefinder that would use triangulation. Although these devices were relatively expensive, crash and crime scene investigators were trying to purchase them.

Bobby Jones, owner of Bobby Jones Accident Reconstruction and Investigation Services in Knoxville, Tenn., points out that the total station is basically a surveyor’s tool that has been adapted by manufacturers for use in forensic surveying cases. At first, law enforcement investigators did not warm up to total stations, thinking they needed extensive surveying skills, according to Jones, who also is a trained accident reconstructionist with the Knox County Sheriff’s Office. However, this thinking has changed. “We still follow many of the same surveying principles in forensic technology,” Jones says. “[But] now it’s called forensic scene mapping, not surveying. We’ve separated church and state.”

An outdoor crime scene spanning two blocks in a neighborhood is mapped with a total station. The total station was able to map spent shell casings and bullet trajectory, among other evidence.

As part of his own professional training, Jones took surveying classes, noting that he observed early on the application of forensic surveying. It was when he became a law enforcement officer that he realized how a total station could be used most effectively for forensic work. Today, Jones is a certified forensic scene mapping instructor for Sokkia and Topcon total stations, among other brands. He has also designed a forensic scene mapping class that is the only university-level class of its kind taught by the Institute of Police Technology and Management in Jacksonville, Fla. Attending these classes are law enforcement officers, surveyors and engineers.

Jones indicates he would “never recommend that a surveyor jump out and try to map a forensic scene,” noting that mapping property for construction or property boundary purposes is different from forensic mapping. “With [forensic scene] mapping, it’s a matter of how well you understand the evidence you’re collecting,” he says. “You may be the world’s best surveyor, but if you don’t have some education on the understanding of measuring forensic evidence, you’ll get crossed out.”

This is why Jones introduces his students to the legal aspects of mapping as well as the technical aspects of how to map a forensic scene. “As a surveyor coming into forensic mapping, you already know how to measure it [the scene] with the equipment, but you might not know how to properly identify it,” Jones asserts.

Although forensic mapping has been around for years, the beleaguered economy and its impact on the surveying profession is prompting many surveyors to closely eye forensic mapping as an alternate field for using their skills. “It’s not a service that’s dependent on the economy necessarily,” says Curtis Sumner, ACSM executive director. “It’s dependent on incidents.”

Sumner, a trained surveyor who previously operated his own consulting business, asserts that the total station is the standard “tool of choice” among forensic mappers due to its ease of use and because it can draw a picture and label a lot of the data “right out of the machine.”

Bobby Jones, a Knoxville, Tennessee reconstructionist and forensic mapping trainer, uses a Sokkia robotic total station to map the scene of a two-vehicle crash.

However, Sumner also cautions that not just anyone can use a total station with a little training. “How that person structures the evidence and records what he collects could have an impact on whether or not it actually provides a true picture,” Sumner says. “The thing that no instrument is ever going to do is take away the ability to analyze the evidence. That’s something that still relies on one’s expertise, education and experience.”

David Hoffart, owner of Transit Works, a Lincoln, Nebraska-based surveying equipment sales and service firm, agrees with both Sumner and Jones. “Learning the proper techniques for operating total stations goes hand-in-hand with understanding the importance of accurately identifying and collecting evidence at a crime scene,” he says.

Indeed, the total station itself has become more highly specialized in its design and operation. Reflectorless, robotic and GNSS/GPS total stations are all used today in forensic surveying. The choice between types and brands often comes down to specific features. Both Jones and Hoffart are staunch advocates of the Sokkia total station. For Jones, the compelling feature was the red dot laser, which the operator uses by aiming the laser beam at the target being measured, then presses a button to pinpoint the measurement. Although most total station makers offer the red dot laser on selected models, “Sokkia was the leader in total stations that had a built-in red dot laser,” Jones says. He also likes the units’ simplicity of operation. Setup entails only about three to four button strokes, even to activate the Sokkia total station’s internal memory or an external data collector. “At 3 in the morning, any one of my students will remember how to level it [the total station], turn it on, and start shooting,” he says.

For his classes, Jones uses the Sokkia 530R3 total station because, he says, it is one of the most affordable long-range reflectorless total stations available. He also uses the Sokkia SRX Robotic Total Stations in his training sessions since it offers more features, has easier setup, prolonged operation and more versatility than any other total station he has used.

There is another reason that Jones finds his choice of total stations compelling. As total station technology has evolved, crime and crash scenes not only have grown in size, but also have been filling up with much more data because it is now easier and more efficient to collect data in large amounts. Says Jones, “Sokkia answered this problem by developing a long-range laser that shoots to non-reflective targets on the roadway within the range of a quarter mile.”

Students attending a forensic mapping class at the Institute of Police Technology and Management in Florida practice operating total stations.

According to Hoffart, Sokkia was savvy enough to know the needs of forensic surveyors and innovative in its design by building interfaces for its total stations to work with multiple instruments. “That really was the trigger for all of the data collection and mapping that we were involved with,” Hoffart says.

Both Jones and Hoffart stress that they open their classes to training on any brand of total station. And they add that they do not promote one brand over another in the classroom.

The payoff with technology advancements in today’s wide range of total station brands and models for forensic work is their speed and accuracy, both of which are critical to preserving evidence being collected. “Every crime scene is dynamic and aging,” Jones explains. “This is why we stress proper evidence identification and encourage students to take courses so that they learn not to disturb the crime scene.”

Hoffart feels equally as strong on this issue. “Once the evidence is picked up, mapped, it’s gone,” he says. “So you’ve got to be efficient in getting out there, getting evidence you need as quickly and accurately as possible, and then getting the site open again.”

The ultimate test for any surveyor entering the forensic surveying field is how to make total station data defensible in the courtroom. This is why Jones covers what he describes as the “weak points” of introducing forensic scene mapping data into cases. “If the defense can destroy your testimony about your measurements, then it’s kind of fruits of the poison tree--everything subsequently goes downhill,” he says. “If they can prove that your measurements are not accurate, or that you didn’t follow certain protocol, or that your instrument was not working properly, they’re going to be able to attack everything that is tied to the measurements, whether it be bullet trajectory or length of a skid mark.”

Classroom instruction on forensic mapping focuses on several aspects, including proper procedures for mapping evidence with a total station and the legal aspects of forensic mapping.

To prevent this kind of case derailment, Jones stresses that his classes train students to learn how their total stations operate. Each student must prove that the total station was working correctly at the beginning of his mapping and that it was still in the same position and working properly at the very end of the mapping process.

Hoffart takes a similar approach in his total station instruction. He also has some additional advice for anyone pursuing or just entering the forensic field. “We advise our students and clients just to go out and map, not wait for their first accident,” Hoffart says. “Get out and use the equipment. Map an intersection or roadway, and see how it looks.”

Just how does a surveyor enter the forensic mapping field? Sumner notes he has observed some surveyors who have developed working relationships with their local government, such as the public works department. This kind of relationship might enable a surveyor to be referred to the police department for his or her services since he or she may already be under contract.

In addition, “Some other surveyors I’ve spoken to have gotten into forensic mapping almost from the other side of the equation, where they get hired by clients who are looking to dispute the findings of the police,” Sumner explains. The dispute is based on the belief that although the police officer knew how to use the equipment (such as a total station), he or she did not necessarily understand what it was doing, or that the officer was not using the equipment in a way that the professional surveyor would.

Nevertheless, Sumner argues, if a crash or crime case goes to court, the surveyor would be called to verify the collection of evidence and that it was done to proper standards. “But he or she really wouldn’t have any say about what the evidence indicated,” Sumner emphasizes. “The surveyor’s job is to show the facts (from a surveying procedure standpoint) without any bias.”

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