3D CRIME SCENE RECONSTRUCTION Clint Fritz August 22, 2010 Devry University CRMJ420ON_B Table of Contents Types of Crime Scene Reconstruction3 Specific Incident Reconstruction3 Specific Event Reconstruction3 Specific Physical Evidence Reconstruction4 Capturing the Measurements4 Quick Record to Preserve the Crime Scene5 Multiple Scans of the scene to create one model5 Calibrated Digital Cameras5 3D Lasers5 Model the 3D Crime Scene6 3D Software6 360 Degree View6 Virtual Tool7 Measure Distances at the office7 Calculate trajectories of blood spatter7
Measurement can be taken at a later time7 Never have to worry about not getting a measurement7 Comparison of Traditional Sketches7 Lack of Information7 Investigators Collaboration4 Test Theories8 Confirm Witnesses Testimony8 Presentation to the Jury9 Virtual Tour9 New technologically advanced 3D computer reconstructions allow the viewer to see real images of the crime scene much like watching a television show. The virtual world can be created using 3D lasers and computer software. The crime scene is taking on a completely different view.
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No longer is the crime scene restricted to inside of the crime tape. It has moved beyond a physical barrier allowing analysts to dissect the crime scene to identify evidence often missed simply walking through the traditional steps of sketching. There is now the opportunity for anyone to revisit the crime scene the next day, next week, or years from now. This is an important function to allow the jury to see exactly what the investigators and witnesses saw at the crime scene leaving nothing to the juror’s imagination.
According to the Department of Safety for the State of Connecticut, forensic crime scene reconstruction “is the process of determining the sequence of events about what occurred during and after a crime” (Department of Public Safety – Scientific Services, 2010). Crime scene reconstruction normally starts ideas of what happened during the crime and then moves to an analysis of the evidence at the scene. It focuses on gathering as much data and evidence to form a valid hypothesis. The hypothesis can then be subjected to various tests to prove or disprove the overall interpretation of the reconstruction.
Once the reconstruction is formalized a theory can be determined in support of the reconstruction. There are three types of crime scene reconstructions. They are specific incident reconstruction, specific event reconstruction, and specific physical evidence reconstruction. Specific incident reconstruction involves reconstructing a crime scene where an accident or incident occurred. This will be needed during such incidences as traffic accidents or homicides. The purpose is to identify the types of evidence that can be associated with these incidents.
Using specific event reconstruction, the sequence of events or timelines can be established. This form of reconstruction looks at how all of the pieces of the puzzle fit together. With specific event reconstruction the sequence of events can be determined. The final type of reconstruction is specific physical evidence reconstruction. This involves evidence such as blood and bullets. Through reconstruction of blood splatter, it can be determined where the shooter was standing during a homicide. It will also help identify the location of the bullet if it is exits the body of the victim.
Capturing the crime scene is an important part of the crime scene reconstruction process. Typical methods include sketching the crime scene using graph paper and a pencil or taking photographs from a digital camera. Both of these methods do provide a snapshot of the crime scene for preservation but, they do not capture the scene in its entirety. A sketch will note measurements of physical evidence in their relation to the victim’s body or to such items as furniture and doorways. However, it is completely relying on the investigator to supply accurate measurements and identification of the physical evidence.
Using 3D technology, the entire crime scene can be analyzed for accurate measurements at anytime. An advantage that 3D technology has over other methods of crime scene reconstruction is that it can preserve the crime scene in a moment in time. This is vital if the scene is in a populated area and needs to return to its natural state as soon as possible. Think about a crash scene involving two vehicles on an expressway in Los Angeles during rush hour that resulted in a fatality. The time it takes to clear the scene is a very important variable when collecting the evidence.
Under these conditions, there may be evidence that goes unnoticed by an investigator that is sketching the scene. Not to mention the time that it takes to do physical measurements. Using 3D technology can allow the investigator to collect the data and have confidence that nothing will missed. In order to capture a crime scene in its entirety multiple scans of the scene must be considered. The collection of data comes from only the viewpoint of the investigator. Consider capturing the image of an automobile.
If we were to stand at the front of the automobile we would not be able to capture the rear of the car. Therefore, the investigator must stand at the rear of the automobile to in order to collect a complete image. One tool used to collect 3D images from a crime scene is a calibrated digital camera. It uses a technology called stereo photography. Standard photographs are only 2-dimensional representations of what you see. 3-dimensional photographs are taken from two perspectives. Because we have two eyes, we will need two perspectives on a scene.
By forcing each eye to see only one photograph, i. e. the left eye sees the left photograph and the right eye sees the right photograph, your brain will reconstruct the depth information from the two pictures and you will see a 3D image (3dphotography, 2010). The use of calibrated digital cameras allows the viewer to see the image as it would have been seen by the individual taking the pictures. When multiple photographs are combined, a reconstruction of the scene is created. Another tool that is used to collect 3D images from a crime scene is a 3D scanner or laser.
A 3D scanner is known for high-accuracy and long range. Most 3D scanners can collect data from 900 feet away. It can operate in bright sunlight or total darkness, indoors or out. The built-in digital camera allows the measured 3D data (known as a “point cloud”) to automatically be mapped creating a 3D rendering of the scene (3D Forensic Mapping, 2010). The 3D scanner quickly digitizes a scene using both panoramic photography and 3D laser scanning which is the process of making millions of highly accurate measurements in just a few minutes.
The result is an accurate 3D representation of the scene from which any measurement can be made, even long after the scene has been vacated. Whether using a calibrated digital camera or a 3D scanner, it is time to create a 3D model of the data. The models are assembled in 3D animation software. This is when the data that was collected at the crime scene is put into the software. In the case of the using a calibrated digital camera, each pixel is assigned a coordinate. The coordinate is made up of XYZ; where X is an Easting coordinate, Y is a Northing coordinate, and Z is the elevation.
The pixels or coordinates are then plotted on a 3 dimensional grid. If we consider a sketch that is typically performed at a crime scene, it is laid out on a piece of graph paper. The investigator assigns a certain measurement between squares and then plots all the relative items of the crime scene at the respected distance. This would be considered a 2 dimensional drawing where only X & Y are plotted. In a 3D plot, it includes the Z value. This gives the 3 dimensional model its depth. So, the multiple photographs taken with the calibrated digital camera are overlaid, assigned a coordinate, and modeled into a 3D image.
The 3D scanner is not much different from a calibrated digital camera, although it uses an infrared laser to collect data points instead of pixels. The hardware then assigns coordinates to each data point and the software plots them. A 3D scanner can collect as many as 100,000 data points per second (Oberle, 2009). This creates a huge advantage over using digital camera which can only collect upwards of 8 million pixels with each photo (Patterson, 2010). It would only take a scanner just over a minute to surpass a digital camera in resolution. At this point, the “scene” is ready or review. With the combination of photo-like images the software will allow the viewer to spin the images 360-degrees. Looking at the computer screen, you will be able to enter the crime scene as if you were actually there. This can be copied and viewed by anyone with access to the 3D software. It becomes a virtual tool that many people can review. The more investigators that can view the crime scene, the more likely evidence will not go unnoticed. When reviewing the crime scene reconstruction, measurements can be achieved right from the office.
Because each data point is assigned a coordinate, the distance formula can be used to calculate distances between two points. The software includes an algorithm that can quickly calculate the distance between any points selected by the user. Therefore, determining specific physical evidence reconstruction such as blood splatter is made possible back at the office. In blood spatter evidence, the measurements will help calculate the mass of each drop from the size of its stain, and use this to calculate its maximum potential velocity.
Air drag would tear apart a droplet if it travelled faster than this limit (Marks, 2010). With that information, and an angle of impact estimated from the shape of the stain, the software projects a realistic trajectory backwards in time to locate the origin of the blood spatter. This is made possible by a crime scene frozen in time. There will never be an issue of not getting measurements before the crime scene is released. Let us review the traditional crime scene techniques. A sketch is prepared of the layout of the crime scene. On the sketch there will be an arrow indicating which direction is north.
It is difficult to make measurements closer than the nearest half-inch, since it is difficult to achieve exact 90-degree angles when using the rectangular coordinate method of measurement or to achieve an exact zero for the triangulation method of measurement (Ogle Jr. , 2007). This can be achieved through the use of 3D scanners. Some errors made when measuring a crime scene by hand could be allowing the measuring tape to sag while recording a measurement, reading numbers upside down, reading the wrong foot mark, confusing the zero point of tape, or reading tenths of a foot for inches while using an engineer’s tape (Ogle Jr. 2007). The margin is much greater when trying to reconstruct the crime scene using inaccurate data. This is not a concern when collecting the data using a 3D scanner and measuring the data points in 3D modeling software. Investigators can gather around and view the virtual crime scene to test their own theories of what actually took place during the crime. A popular show on A;E television is Crime 360. There is an episode where criminal investigators have a theory of how a victim was shot (A;E, 2009).
The scene shows three investigators gathered around the computer monitor reviewing the 3D modeled crime scene. They used the pictures of the blood spatter to determine the location of the shooter. Once they entered into the virtual world they quickly realized the shooter could have bent down on one knee and shot from behind a row of shrubs. This would have helped the shooter remained unseen. The investigators then rotated the scene to see if any of the homes across the street could have been able to see the shooter.
It was identified that someone across the street could have seen the shooter running away from the scene. From this information they identified the resident and confirmed that she saw the man leaving the scene and gave a description of him. This virtual world allows many different scenarios to play out until the correct one is revealed. As physical evidence is collected from the crime scene so is testimony from eye witnesses. Investigators take down the testimony and then try to confirm it by situational and physical evidence.
Entering the virtual crime scene allows the investigator to confirm or throw out the testimony. For example, in a case in 2009, a 3D reconstruction of the crime scene was used with photographic evidence to examine the dynamics of an alleged sexual assault. Comparative grids were made which put together the statements made by witnesses, which were useful in making an accurate assessment of the testimonial credibility of the woman accusing the defendant (Strano, 2009). Jury sitting on a trial will not have any knowledge of the case in which they are about to hear.
Therefore it is important for the prosecution to have a way to lay out the crime in a way that they can understand. With 3D virtual animation, the jury can enter the crime scene and see firsthand how the prosecutor has pieced together the crime. The animation software allows the prosecutor to put together a virtual tour of the crime scene (Capture, 2010). Most everyone can accept what they see more than what they hear. The virtual tour of the crime scene is undisputable and can reveal credibility to the prosecution’s evidence.
In conclusion, the use of calibrated digital cameras and 3D scanners can allow investigators to revisit a crime scene any time they want. The data collected at the crime scene can be stored or shared for many years. It will allow for cold cases to be reopened and enter the crime scene just like it was yesterday. This is an extreme advantage when it comes time to present the evidence to a jury. The virtual tour of the crime scene will visually assist in identifying the events of the crime. References 3D Forensic Mapping. (2010). Retrieved August 15, 2010, from Leica Geosystems. s: http://www. leica-geosystems. us/forensic/3d_scanning. html 3dphotography. (2010). Retrieved August 8, 2010, from 3dphoto. net: http://www. 3dphoto. net/ A&E (Director). (2009). Crime 360 [Motion Picture]. Capture. (2010). Retrieved August 22, 2010, from mapscenes. com: http://www. mapscenes. com/capture/viewer/viewer. htm Department of Public Safety – Scientific Services. (2010). Retrieved August 8, 2010, from CT. gov: http://www. ct. gov/dps/cwp/view. asp? a=2155&Q=315024&PM=1 Marks, P. (2010). Blood spatter model to help crime scene investigation.
New Scientist , 20. Oberle, P. (2009, October 12). 3D laser scanner. Retrieved August 15, 2010, from knol: http://knol. google. com/k/3d-laser-scanner# Ogle Jr. , R. R. (2007). Crime Scene Investigation & Reconstruction. Prentice Hall. Patterson, S. (2010). Image Resolution And Print Quality. Retrieved August 15, 2010, from photoshoessentials. com: http://www. photoshopessentials. com/essentials/image-quality/ Strano, M. (2009, April). Carlo Parlanti Case. Retrieved August 22, 2010, from carloparlanti. com: http://www. carloparlanti. com/MarcoStrano/Marco_Strano. pdf