3D Laser Scanning Techniques for the Crime Scene Investigator
Written by Brenda Butler   

THERE ARE SOME SITUATIONS that require high-detail scanning. When scanning point of impact, trajectory rods, bloodstain patterns, or anything else that requires very high detail, scan your scene on the determined scene settings and then obtain high-resolution and high-quality scans at a setting of at least 1/4 resolution and 4x quality (if color is applied). Alternatively, after a scan is complete, you can add clusters that include the high-detail area. This reduces your horizontal and vertical angles to allow a high-resolution scan of the specified item within a shorter period of time.

This article is the second in a series intended to answer many of the questions that are continually asked of the author as a forensic solutions specialist for FARO Technologies. The author has more than 20 years of experience as a police officer and 14 years as a crime scene investigator and evidence technician. This article series will provide helpful techniques and best practices compiled from the author’s experience and the experience of other crime scene investigators across the United States. Even though the technique examples may refer to the FARO laser scanner, the scanning techniques can be utilized by anyone who has a 3D laser scanner and may be applied to any scene, regardless of the manufacturer. Remember, it is always best to refer to your manufacturer’s guidelines and your agency’s protocol when determining the best scanning methods for your specific scanner.

Find Part One: Planning and Positioning of the Scanner in the Fall 2019 issue and Part Two: Executing the Scan in the Winter 2019 issue of Evidence Technology Magazine.

Documenting Bullet Impacts
Documenting and scanning bullet impacts for future analysis requires the impacts to be identified on scene and trajectory rods inserted into the applicable impacts. I recommend you identify all bullet impacts according to your policies and procedures (i.e., BI 1.0, BI 1.1, BI 1.2, etc.), utilizing stickers to identify the bullet path. If the bullet impact is re-constructible, insert trajectory rods or rods with spheres. A qualifying impact point requires two points, such as an entry and an exit or an entry and a secondary impact point. All shooting-incident reconstruction rules apply here.

Once the bullet impacts are identified and the trajectory rods are in place, scan the trajectory rods using high-detail scanning, or by manually setting your parameters to a minimum of 1/4 resolution and 4x quality. Make sure you place your scanner a reasonable distance from your trajectory rods to capture the needed points. Remember, the scanner has a diameter below it that does not collect data, and if the scanner is too close, it will not collect the data of the trajectory rod. Conversely, do not scan too far from your trajectory rods, or the resolution setting will prevent the scanner from collecting enough data points on the trajectory rod. Color or grayscale scans both work very well for trajectory rods. Make sure you are greater than 45° to the trajectory rod; 90° is preferred if you are not using spheres. An option is to add a high-detail scan of the rods by adding a cluster to the scan. You can determine if you need this by checking your initial scan to make sure you captured the trajectory rod.

After you scan your scene and import, process, and register your project, the project point cloud can be brought into forensic analysis software and the shooting trajectory tool can be used to reconstruct the shooting incident based on the bullet impacts you selected and identified at the scene. This provides the horizontal and vertical angles of the bullet path and the X, Y, and Z of the bullet impact (location in scene).

Reconstructing a shooting incident can answer the question of where the muzzle of the gun was when it was fired. It can also assist in determining if there were multiple shooters or a moving shooter. As an example, the FARO Zone 3D forensic-analysis software produces a reconstruction report that can be printed and analyzed by an expert. The shooting trajectory tool does not replace the required training in shooting incident reconstruction and does not permit a non-qualified expert to render a conclusion in court. Training and peer review are requirements of any expert analysis, and I recommend you have your report peer reviewed as well.

Documenting Bloodstain Patterns
Documenting and scanning bloodstain patterns for future analysis requires the bloodstain patterns to be identified and mapped according to your agency’s policies and procedures. Identify which bloodstain patterns meet the criteria for bloodstain pattern analysis. Bloodstain pattern analysis rules apply here, and at the very minimum I recommend basic pattern-recognition training. You need to know which stains you should document for future analysis.

The type of patterns used for analysis are spatter patterns — unique patterns that are created when a force greater than gravity strikes blood, and the force causes the blood to disperse in a radiating distribution, upward and outward from the point of the impact. These are used for analysis because it is possible to look at the size, shape, and distribution and measure the qualifying bloodstains, using mathematical calculations to determine the point of the bloodstain’s origination. Identify bloodspatter patterns that qualify for analysis. Make sure to avoid spatter stains resulting from parabolic flight. Do not use any bloodstain below the 90° horizontal plane (going downward). Do not use cast-off bloodstains (bloodstains in a linear pattern that were released from a hand or weapon during movement).

Identify your qualifying bloodstain patterns. Label the overall bloodstain pattern according to your agency’s policies and procedures (i.e., A, B, C, etc.). Use a marker, pencil, or sticker on the surface to identify the bloodstain pattern so it is visible in your photographs and so that the scanner can capture it. Label individual bloodstains that are determined to be excellent candidates for analysis (i.e., A1, A2, A3, etc.). The more you identify, the greater the accuracy of your area of origin upon completion of your analysis. Make sure you identify the bloodstains from a radiating distribution. Do not use bloodstains from only one area, section, or side. If you are not comfortable identifying the individual bloodstains within the pattern, this step can be skipped — but it will make it a little more challenging in the software to determine exactly which bloodstains you are identifying within the pattern when it comes time to testify in court.

Next, add two markers horizontally on the bloodstain patterns if you plan on using 3D software to perform a bloodstain analysis later. Markers can be a circle you draw on the surface, a scale with a mark on it, or any other item where you can be precise in selecting a specific point in the software. Make sure your markers are on the outer left and outer right edge of each bloodstain pattern. If the bloodstain pattern is large, add another marker horizontally in the middle of the pattern or grid it off, with each grid having two horizontal markers. If gridding it off, horizontal markers should overlap. In other words, use the same marker for the connecting bloodstains.

Once you have finished labeling the bloodstain patterns, take photographs of them. This is needed for analysis if you are using FARO Zone 3D software. Your photographs must be 90° to the bloodstain (i.e. they cannot be angled) and must be a macro photograph of the bloodstain. Do not angle it downward or upward, as this can alter the appearance of the bloodstain. It must be in focus and very clear. It is best to use your camera in manual focus, as this gives you total control. Your camera’s autofocus may focus on the surface and not on the bloodstain, causing blurred edges of the stain that can inhibit your analysis. Use a tripod, if necessary, to obtain the best camera focus. Fill the frame! Crime scene macrophotography rules apply. The left and right markers should be on the very edge of your photograph when you look through the camera. Photograph individually labeled bloodstains in the event your overall bloodstain picture has a blurred edge on a bloodstain. The individual photograph can be utilized in the software in addition to the overall pattern.

After you have identified, labeled, and photographed the bloodstain patterns that you determined were qualified for analysis, you are ready to scan. Make sure you are capturing a high-detail scan of that pattern. I recommend collecting DNA swabs of the bloodstain patterns you intend to analyze, as this can aid an expert in obtaining a conclusion of the events that took place. Scan blood in color if you are able. If you need to scan in grayscale, check your scan after it is finished to make sure the blood in the scan is scanning in infrared. Infrared photography rules apply. As previously stated, blood acts uniquely under infrared. Scan the bloodstains using object HDR scanning or by manually setting your parameters to a minimum of 1/4 resolution and 4x quality. Place your scanner a reasonable distance from your bloodstain to capture the needed points. Remember, the scanner has a diameter below it that does not collect data, and if the scanner is too close it will not collect some of the bloodstain pattern. Conversely, do not scan too far from the bloodstain pattern in relation to your resolution setting, or the point spread will be far enough apart to prevent the scanner from collecting enough data points on the bloodstains.

The project point cloud can be brought into 3D software, such as FARO Zone 3D, and the bloodstain analysis tool can be used to analyze the bloodstain patterns. This provides the area of convergence (2D location) of where the victim was when they shed blood, and it provides the area of origin (3D location) of where the victim was when the victim shed blood. This forensic tool can also assist in determining if the victim was ambulatory when shedding blood by locating multiple areas of origin. The photographs that were taken of the bloodstain patterns and bloodstains can be inserted into the point cloud to allow the bloodstain tool in FARO Zone 3D to determine the length, width, and direction of travel of the bloodstains, and make the potential determinations.

Some 3D software, such as FARO Zone 3D, produces a reconstruction report that can be printed and analyzed by an expert. The calculations have been peer reviewed and are more accurate than human calculations. The bloodstain analysis tool does not replace the required training in bloodstain pattern analysis in order to permit you to render a conclusion in court. The training and peer review are requirements of any expert analysis, and I recommend you have your report peer reviewed, as well.

Summary
This article is intended to provide the novice user with guidelines that can be utilized in many of the situations that are likely to be encountered at the crime scene. Using these guidelines, the crime scene investigator can achieve the best 3D diagram possible, preserving the scene for courtroom presentation.

You may be an experienced scanner operator and may have found your own methods of scanning that work for you. I encourage you to continue doing what is working for you. I do ask that you share your knowledge. Teach your co-workers, peers, and subordinates. Training is sometimes difficult to obtain, and one day the people you teach may be the ones picking up the scanner box instead of you. You are the most valuable tool to your agency with your experience and your knowledge, but if your knowledge goes unshared, it will one day lose its value. Sharing your knowledge will in turn allow your best practices to continue to create excellent court diagrams for those who follow you.

The most important best practice I can share with you is to never become stagnant. Continue training and learning. This article will one day be obsolete, as the technology will advance and continue to evolve. Take advantage of free training options, tutorial videos, self-paced learning, workshops, and user groups. Do not simply get your basic training and stop. Eventually the technology will outpace you.

And finally: Practice! If you are fortunate enough to not have many crime scenes a year, the worst mistake you can make is to put the scanner in a closet and leave it. These are use-them-or-lose-them skills. Take it out and practice scanning and producing a court-deliverable product. Watch a video or attend a user group. Just keep practicing and improving your skills and your level of comfort. The more comfortable you are, the more confident you are, and confidence is important when you are a witness on the stand and the jury is looking to you for answers.


About the Author
Brenda Butler
is a private consultant and a former commissioned police officer. She is a state-recognized expert in multiple Ohio counties in areas of investigation, crime scene investigation and reconstruction, 3D laser scanning, bloodstain pattern analysis, and shooting-incident reconstruction. She has processed countless homicide scenes, officer-involved shooting scenes, and everything in between. Butler has worked as a police officer in Ohio for 20 years and a crime scene investigator for 14 years. She is a graduate of the National Forensic Academy Section XXXIV and has a Master’s Degree in Justice Administration from Tiffin University, as well as a Bachelor’s Degree in Executive Public Safety Management (summa cum lade) from Cleveland State University. She served in the United States Army (military police). Among other certifications, Butler is a certified crime scene analyst with the International Association for Identification and is a previous deputy director and instructor with the Ohio Peace Officer Training Commission. She is an experienced college instructor and has trained hundreds of police officers on a multitude of topics. Butler currently works as a forensic solutions specialist at FARO and has taught 3D laser scanning and crime scene documentation to police agencies across the United States.

This article appeared in the January-February 2020 issue of Evidence Technology Magazine.
You can view that issue here.

 
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