Crime Scene Diagramming and Reconstruction by Det. Mike Anderson

Crime scene diagramming and reconstruction

Detective Michael S. AndersonUnified Police of Greater Salt Lake County

Office 385-468-9821Cell 801-884-9398


• Measuring methods

• A discussion about the methods

• Scene considerations

• Reconstruction methods

• Software's to be used & Equipment calibration

• Court testimony

Crime scene diagramming and reconstruction. Measuring methods

• There are several ways to document any crime scene for purposes of preservation and reconstruction.

• The first method has been around for all of us the longest and that simply is hand measuring.

• This can be an effective way to produce a scale scene diagram, however this method needs careful consideration in the measuring process

Crime scene diagramming and reconstruction. Measuring methods

• Since you will not be utilizing modern technology in this process you will need to measure on the X, Y, and Z axis yourself. Careful recording of these measurements will be crucial in the event you have a need to produce a 3D scale diagram later.

• Processing this scene using the triangulation or Coordinate method will produce the results you are desiring.


• Example of Triangulation method


• The triangulation method simply works by taking two measurements of any one point from two known locations.


• The other option for hand measuring a scene is the Coordinate method.


• The Coordinate method for many is a little easier to deal with, and use. This method is in some opinions easier if you aren't use to measuring by hand.

• This method is just as accurate, so long as you are accurate in the execution of the measurements.


• To measure using the Coordinate system you will measure off of two locations known as the RP and the Baseline.

• Always a good idea when measuring by hand or any other method for that matter to have good scene pictures to help verify locations of items identified for your diagram and eventual reconstruction.


• The next method, and at one time a very common way of diagramming a scene is the use of Photogrammetry.

• Photogrammetry is a relatively inexpensive way to diagram or measure anything by way of using digital pictures.


• A simple explanation of Photogrammetry is that by way of taking a particular set of pictures of anything can result in a 3D rendering of that item or scene, However these pictures are very specific in nature, but extremely effective.


• One of the most accurate and common ways to survey any scene to date is the use of a total station, or a series of total stations for any scene which needs to be accurately measured.

• Just like in Photogrammetry every point recorded by the operator has the X, Y and Z coordinate registered.


• Also like any of the previously mentioned method this is as accurate as the user is.

• And is as detailed as the user wants to make it be

• Any scene by way of this method can be reconstructed in 2D, or 3D. Depending on the needs of the case.


• There are many types of Total Stations on the market.

• Sokkia

• Leica

• Trimble

• Nikon

• etc


• There are a couple ways to survey using a total station

• One is direct shooting and logging the data you survey directly into the gun itself

• The other is to survey into a data collector using collection software which is similar to the drawing software you already use.


• From a law enforcement perspective its my belief that surveying by way of a data collector is the best practice

• For the most part law enforcement officers aren't professional surveyors, and therefore the likely hood of a costly mistake can, and will increase.


• The fact of the matter is this method gives us the best chance at good results.

• By using a data collector you have the advantage to see the collected data as you go.


• Having the ability to see your scene as it is measured gives you the advantage of seeing where things are missing, as well as a major advantage by increasing the overall accuracy.

• If you are already surveying without a data collector and you are comfortable doing it this way then no worries

• Do what is familiar, and what you are comfortable with


• And one of the newer methods to all of us is the use of 3D laser scanners.

• There are several scanners available now

• The two most commonly known and used at this time are the Leica scan station.


• And the other is the FARO 3D laser scanner.


• This method of measuring is not only the future, but it is our present.

• There are numerous Law Enforcement agencies from coast to coast that have embraced 3D scan technology.

• This is the most accurate method available right now for us to measure a scene.


• And it’s the best way to preserve a scene for life.

• The laser scanner to explain it simply is mapping and measuring everything that your eye sees.


• As you look at these images realize that the images are produced by laser mapping data.


• Laser scanning can be set up to take millions of points per minute.

• How long would it take us to survey a million points by hand measuring, Photogrammetry, or even our total station’s?

• Laser scanning works much in the same way as a total station does. We set up and we scan. When we do this we have known common


• reference points ahead of us so that scans can be merged together to create a single scan or survey product.

• No matter how you are mapping and diagramming your scene .

• The most important thing is that you know how to explain the work that is done.

• And that the work done is accurate and correct.

Crime scene diagramming and reconstruction. Crime scene

considerations• Wherever he steps, whatever he touches, whatever he leaves, even unconsciously,

will serve as silent evidence against him. Not only his fingerprints or his footprints,

but his hair, the fibers from his clothes, the glass he breaks, the tool mark he leaves,

the paint he scratches, the blood or semen he deposits or collects - all these and

more bear mute witness against him. This is evidence that does not forget. It is not

confused by the excitement of the moment. It is not absent because human

witnesses are. It is factual evidence. Physical evidence cannot be wrong; it cannot

perjure itself; it cannot be wholly absent. Only its interpretation can error. Only

human failure to find it, study and understand it, can diminish its value.

• Kirk, Paul,

• Crime investigation,

• John Wiley & Sons Canada, Limited, 1953


considerations• When we are just entering or we have been in

the scene for a time, we need to always be mindful of the situation

• What is at our feet at all times, how many evidentiary, or potential evidentiary items have we stepped on, kicked, or destroyed while we were present in a scene.


considerations• Every time we become complacent in a crime

scene the potential to contaminate a key piece of evidence increases

• Losing a case to a situation such as this is not likely something any of us want to face.

• So what are the proper steps and considerations we should make while the crime scene is processed and the scene is measured or surveyed


considerations• Before measuring of the crime scene begins, the

scene as it sits should be documented.

• The best way for this is good proper overall pictures, as well as a good walk through and surrounding video.

• The simple reason for this is to have record of the location of everything in the scene in the event something does get moved, or even needs to be moved intentionally for any reason


considerations• In cases where something needs to be moved

it is a good idea when possible to mark the location of the item to be moved as well as pictures and video of the item prior to movement

• When possible an actual survey measurement of an item being moved should be taken prior to any movement, but that isn't always possible


considerations• Sometimes we just need to be flexible in how

things are done, but we should never veer from what needs to be done

• Corner cutting and unwillingness to do the work is never excused in these matters


considerations• Much of this process is going to be dictated by the

individual agencies policies and procedures.• However minimizing any scene to outside influence will

always be the best practice.• Limiting the possibility for evidence to be spoiled or

tampered with is a desired result.• Having control of the scene is also important. simply

because a ranking officer shows up on scene and wants to go inside and look around isn't a good enough reason to enter. Remember it is you who has to testify to this scene and its validity not the lookie loo administrator etc.


considerations• Once the scene has been processed and evidence

has been identified, the scene should then be marked.

• This can be done by way of yellow evidentiary markers, or what ever marking process your agency has adopted.

• At this time the scene should now be re documented by way of pictures and video

• It is also a good idea to complete a field sketch of the scene.


considerations• This process helps to validate that the scene

has not been changed from first entry.

• Once the pictures and video process has been completed for the second time, you have now reached the time to document the scene.


considerations• From here the process really depends on what

your method of documentation is going to be.

• For instance does your agency prefer to collect all the identified evidence within the scene prior to the measuring and documentation process?

• If so there are some things to really consider here.


considerations• By measuring a scene without the evidence still in

place, all your measuring is the location of the evidence markers now.

• And is not necessarily the actual location of the identified evidence.

• So does this matter?

• Well it may. Again the fact is you are the collector of this data, and it will be you who has to testify to the validity of the measured data regardless of how the measurements were taken.


considerations• Again individual agency policies will have the

final say in how this is completed, however it is a good idea to always measure with the placards or markers and the evidence still in place.


considerations• Remember two of our current methods of

scene measuring are depicting the scene in a photo type manner such as 3D scanning and Photogrammetry. From these two methods alone anyone can see that evidence itself is missing during the measuring process.

Crime scene diagramming and reconstruction. Some reconstruction

methods• There are a few things to consider when

reconstructing a crime scene.

• First is what are you wanting, or needing to show in this reconstruction?

• Many times simply showing the scene in a top down 2D format, or view is all that is needed.

• Many times these diagrams are simply being used to take measurements of evidence of location, and items.


methods• Or they are used to show an overhead view of

the scene and it’s evidence.

• If a 2D drawing is all that is necessary or needed then we simply need to plug our measurements into our drawing software.

• Rather this is done by inputting hand measurements, or we are inputting that data through a hand held device such as data collector from a total station survey, or point cloud data downloaded from a 3D scanner.


methods• Either way the source of the data really

doesn’t matter.

• Once this data is in place a simple 2D drawing can now be completed by way of connecting the line points, and dropping in place the evidence and the related placard numbers.

• These 2D drawings can be as simple as a black and white line rendering.


methods• To an elaborate depiction using colors and

textures.

• No matter how detailed you want to be the most important thing in any drawing is going to be the accuracy, and reliability of the producing data.


methods• Elaborate scene drawing


methods• Simple scene drawing example

Crime scene diagramming and reconstruction. Software options.

• To create these drawing you will need some type of software to achieve this.

• So what software to use?

• The fact is there are many choices, and the best one for you, is for you to decide.

• Do your research when it comes to software. What are your needs going to be, and what are your capabilities to collect and use this software?


• There is no reason to spend thousands and thousands on a software that does many things that you don’t have the capability to utilize.

• You also don’t want to buy an inexpensive lesser software that doesn’t take care of your needs based on your capabilities.

• Too many times especially in law enforcement we get stuck in the mind set that if we can do it cheaper then that is our route.


• However it does no good to not be able to conduct your business as needed.

• So spending the extra to do what is necessary is the best option even though it will cost more.


• So what is out there?

• Many of us are users already of this company’s product, crime zone crash zone has been around a long time.


• ARAS 360


• Visual Statements FX3


• EDGE FX


• Autocad


methods• You also may have a need to have something a

little more elaborate.

• Such as representations in 3D

• Or scene fly through representations etc.


methods• 3D drawing views or videos can allow you to

place a judge or jury in the scene.

• even if the scene no longer exists.

• These views can also be extremely helpful in an investigation

• They can help an investigator see what the actual view would have been for a witness or victim etc.


methods• Bullet trajectory example from FARO scan data


methods

• Scene fly through examples

• These examples were created in the SCENE software. This is the FARO cloud managing software specific to FARO.

Crime scene diagramming and reconstruction. Court Testimony.

• At the end of the day what we are after is a suspect conviction.

• All the work done by the investigators, the crime scene personnel, and the prosecutors is to build a strong prosecutable case.


• So as the documenter of the scene, it is our job to do a good and accurate rendering of the scene, the evidence, and anything else that needs to be captured.

• Making sure that all of your measuring equipment which you rely on is at a minimum annually cleaned inspected and calibrated.

• It doesn’t matter if you are using a rolling tape measure to a laser scanner. This cannot be skipped.


• The validity of the data is going to be the first line of attack for a defense attorney.

• Always have on hand with you in any court proceeding the documentation of your measuring instrument and its calibration.

• Do not find yourself trying to explain this on the stand without being able to produce it when asked to.


• And always remember you only know what you know.

• Always stick to the facts as you know them to be.

• If you don’t know something that is ok, never assume to know facts when you don’t.

• And always tell the truth even though a truthful answer may be hurtful to the case.

• Your career, family, credibility and livelihood are far more important than this case.

The End

Presentations & Public Speaking

Crime Scene Diagramming and Reconstruction by Det. Mike Anderson