By Frank J. Hahnel III, Feb. 13, 2014
When taking the witness stand, it is imperative to be as prepared as possible and ready to present your scan data in an effective and concise manner. This preparation begins long before you take the stand. It begins even before you even step foot on the crime or accident scene. To ensure your data has what it takes to stand up in court, put the following 10 key elements into practice.
1. Use a NIST traceable validation tool during the collection process at the scene.
In scanning applications, a NIST traceable validation tool, such as Leica Geosystems’ Twin Target Pole, verifies that the laser scanner is working according to established tolerances. This is critical because whether using a total station, a GPS unit or a 3D laser scanner, variables can be introduced that may cause your measurements to be erroneous. It’s a recommended best practice to have a NIST traceable validation tool on the scene to verify that the laser scanner is accurate, problem-free and operating within its normal parameters before scanning. The NIST traceable validation tool can provide additional benefits when validating the accuracy of calculations derived from the data using software programs. Without the certified distance standard and the correlating certification report, it may be more difficult to defend the accuracy of your work and, as a result, your data may be declared inadmissible during court proceedings.
2. Review the registration report.
A registration report states the overall accuracy of the registration when multiple scans are combined into a single coordinate system. If scans are not registered with good precision, then the accuracy of measurements will be negatively affected. Always review the registration error report for your scan data to ensure that any errors are within acceptable tolerance. It may be helpful to have the report printed out and readily available to prove the accuracy of your data. Detailed registration statistics should include any error for each target constraint as well as the root mean square (RMS) error and error histogram for each cloud constraint.
3. Use a scanner floor stand for evidence on the ground.
A laser scanner operates on line-of-sight. Therefore, certain vantage points will be unavailable when using the tripod mount. For evidence on the floor or near ground level (such as a weapon underneath a car), mount the scanner on a floor stand. This lowered line-of-sight will enable the scanner to get much closer to the evidence and capture even more detail, which may prove very important in court.
4. Have all of your necessary measurements created in layers and turned off in 3D point cloud processing software.
When taking the witness stand, be prepared to answer all measurement questions that are likely to come up. All measurements considered important to the case should be created ahead of time and assigned to a layer in 3D point cloud processing software that allows layers to be turned on and off. When asked for an anticipated measurement, simply turn on the visibility of the appropriate layer. If asked for a measurement that was not anticipated, you can easily select the corresponding points and retrieve the measurement in real time. However, it is always best to have important measurements created in advance with layers.
5. To improve appearance, unify your point cloud data in 3D point cloud processing software.
High quality 3D point cloud processing software provides a complete set of tools for quickly and accurately unifying point clouds that have been registered. This unification helps computer graphics hardware to display the data, which, in turn, improves the appearance of data viewed in court. Look for software that has the capability to handle and display all collected point clouds, and avoid software that decimates data as a means to handle large point clouds.
6. Ensure ahead of time that your laptop will connect correctly in the courtroom.
This is a simple but very important point. You don’t want to arrive the day of trial and discover that the courtroom doesn’t have the proper connection needed to display scene data from your laptop or desktop computer. While it is best to display the data on a large television or with a projector, the court may not have this equipment available. Visit your courtroom in advance or verify with the attorneys that the necessary equipment is on hand.
7. Have copies of your CV and forensic training certificate available for court review in addition to case particulars where scan data has been accepted in court.
When you are on the witness stand, you may be asked about laser scanning precedents in other court cases. Instead of relying on memory, have the information in front of you so that you can provide case particulars where scan data has been admitted in court.
Additionally, have your curriculum vitae, or CV, with you on the stand. While this may be a no-brainer for experienced professionals, its importance may not be as obvious to a first-time witness. Likewise, have a copy of your forensic training certificate to confirm that you have been trained on the laser scanner and have passed an examination. The training and examination should be administered by qualified trainers with relevant expertise in forensic investigation. The certificate proves to the court that you have demonstrated knowledge, skill and ability with the technology and that you can use it in a proficient manner on a crime scene.
While documents addressing precedent-setting court cases help to uphold the admissibility of the technology, the forensic training certificate and CV serve to verify your credibility and qualifications. These become especially important when the defense is trying to attack your credibility. If they cannot attack the scanner and the technology, the next logical step is to attack the methodology and the individual who processed the scene. The defense’s success in disqualifying any one element can lead to the dismissal of your evidence and, possibly, the case.
8. Generate a 3D visualization presentation for the courtroom.
A 3D visualization presentation is an excellent way to show the judge and jury what happened at the scene. Your software should have the capability to create an interactive panoramic view that allows even nontechnical users to easily view, pan, zoom, measure, and mark up point cloud data over the web via Internet Explorer. In essence, 3D visualization software creates a user-friendly, interactive presentation of the scene for court.
9. Generate a fly-through of the scene from the point cloud data.
Use 3D point cloud processing software to create a short movie clip depicting a 3D fly-through of the scene. Unlike the 3D visualization presentation mentioned previously, a fly-through is not interactive. It follows a set path for a set time and creates a visual walk-through of the scene. The creator of the fly-through can concentrate on specific areas, including key evidence, and identify them within the movie clip. In some cases, it may be better to present a simple fly-through instead of an interactive presentation in court.
10. Create hotlinks in the 3D visualization presentation for scene photographs, video surveillance and any other necessary documents.
The software used to create your 3D visualization presentation should allow for the creation of links to other relevant case information such as documents, photographs, and audio and video recordings through hyperlinks. This is a very useful and important feature when testifying in court. If, for example, the coroner’s report on the victim is available, a hotlink can be created on the victim’s body. Double-clicking the link allows the report to pop up and display cause of death. With this important hyperlink feature, you literally have a database of the crime scene at your fingertips when testifying in court.
Preparation is the key when it comes to testifying in court. By incorporating these 10 key elements into your routine, you can take the witness stand with confidence knowing that your laser scan data will be acceptable and valuable in court.
For more guidance on how to ensure your laser scan data will be acceptable in court, please contact us.
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About the Author: Frank J. Hahnel III has been laser scanning since 2000 and is an expert in the use of Leica 3D laser scanning systems. He has worked with multiple state and local law enforcement agencies and private accident investigation and reconstruction firms, helping them to scan, process and reconstruct active accident and crime scenes. After the September 11th terrorist attacks, he aided the Army Corps of Engineers at Ground Zero in New York and the FBI at the Pentagon. He then assisted the NYPD and FBI with the laser scanning of the debris piles from Ground Zero at the Fresh Kills Landfill, the story of which was published in Professional Surveyor Magazine in 2011. He is a member of the International Association for Identification, International Association for Counterterrorism & Security Professionals, the International Association of Chiefs of Police, and the National Association of Professional Accident Reconstruction Specialists, Inc.