Driving to the crime scene is the time to begin to think of the different types of processing thta may be required. This section will speak about some of the basic crime scene procedures we may face, and with the responsibility of the first responders at the scene.
Processing a crime scene begins the moment you begin your response. As you respond to the scene you should be thinking about the type of crime scene you have, is it a rape, a murder or a break-in. The type of scene we have will help determine the type of equipment needed to do the job: will weather conditions cause us to alter our approach or cause us to collect the evidence out of the normal order of basic crime scene processing?
There are bacially five steps I follow when I have the time, and weather conditions in my favor, to process a crime scene. Once on scene I find it beneficial to talk to the first responding officer about what he observed on his approach. This is the first step: interviewing. We should always make it our policy to ask the first officer on scene questions that will aid us in our ability to process the scene. What did he see? Did he move anything? What time did he arrive?
It is also helpful to have the officer seal off the scene as soon as possible to preserve the intregrity of the scene; obviously the safely and concern for the injured remains first priority. Remember-the crime scene tape does not define the size of the scene. It can always become larger or smaller depending on the evidence located. It is always best to start large, we can always down size to fit our scene.
In regards to the interview, and when available, I like to speak to the victim to get additional information that will help me determine what will or will not need our attention. Were any containers moved, or other items disturbed that may need to be processed? Become comfortable with asking the necessary questions that will help you with processing of the scene. At a crime scene I like to think like the criminal and try to image where I would put my hands (or feet) if I were the one breaking into a residence or business. By processing these areas you may become surprised by the results.
Examine the scene is the second step in processing the scene. Look at your scene- what do we need to collect or consider as evidence. When I speak of examining the scene this refers to an initial walk through with our hands in our pockets. We are only looking at this stage and determining a route in and out of our scene. What do we see? What don't we see? Sometimes it is the lack of evidence that becomes more important then the evidence we see that will help explain our scene.
Next we want to Photograph the scene. I normally use a digital camera to photograph my scenes, but which ever camera you use be sure to photograph your scene from three different perspectives, long range, mid range and closeup (with and without scale). Photograph your scene and your items of evidence in-situ.
We want to do a rough sketch of our scene before we begin the actual duties of processing. This sketch depicts the scene and the items of evidence we are going to collect. Be sure to put north pointing up and, along with our case number, date. address and initials, do not forget to include "not to scale" on our drawing.
Now we are ready to process the scene. Here we use, at our disposal, any and all types of equipment to aid us in the recovery of physical evidence at the crime scene. Be careful and take your time. Here is our area of expertise that can make or break our case by how well be do our jobs.
Once we complete our assignment, I find it good practice to do a final walk through of the scene, usually with a fresh set of eyes to help me determine if we have done all we can do. Remember-once we release the scene -any evidence that was not observed, nor collected, is of no value to our investigation. It may be of benefit to hold on to the scene until all the information is obtained, as an example, the autopsy report may help us focus on an area to search for additional evidence. Each scene will dictate whether to release or not.
Let's look at some of the ways we will process the scene, and the different types of evidence we may find within. We will start with fingerprinting, although this is the last task we want to preform on scene.
Basic fingerprinting techniques involves different mediums. One such medium is black powder and nylon brush. This approach to fingerprint processing is probably the most common, but other mediums are just as effective, and are dependent on the type of substrate, or surface you have.
For example, on most smooth surfaces where black powder is used, clear lifting tape and krome-coat fingerprint card is the best way to lift and preserve this print. I find that the krome coat card and volcanic dark black powder gives the best contrast on most surfaces encountered at a crime scene. Other substrates may require photography as the best way to preserve a print, although I would recomment taking photographs of the prints before any lifting is attempted. Another medium that works well on rough woods or styrofoam surfaces is mikrosil casting material.
While there are many mediums we can choose from to do our job, the point here is: be sure you recognize the type of surface you have to work with and decide which lifting medium will be the best to do the job.
Before we use any medium (powder, chemical, cyanoacrylate ester fuming) to process our evidence. it is always a good idea to follow the safey guidelines or policies of your agency. These guidelines are for our protection, and can keep us from making a serious or fatal mistake. When using chemicals, it is advisable to dip your items in a chemical wash to avoid splashing or inhaling sprayed fumes. Always wear PPE equipment and respirator when dealing with harmful chemicals read the warning labels before beginning.
Smooth surfaces (glass or smooth painted surfaces) black powder and tape are a good choice.
Paper products usually require the use of certain chemicals, such as ninhyrdrin or indane dione, for best results. This type of processing should be preformed back at your lab, and under good ventilation and controlled conditions. Another approach to paper processing is the use of magnetic powder, but I would use caution before making this choice.
On smooth cardboard surfaces I find that magnetic powder does a good job.
Rough wood surfaces, the medium and the lifting method will need to be evaluated. On unpainted wood, especially smooth surfaces, ninhrdrin is a good choice. On rough wood, black powder, then mikrosil may be the best method available.
Styrofoam surfaces (cups, plates) magnetic powder and white mikrosil is a good combination here.
Wet surfaces- I use SPR spray. This will develop a print in wet conditions, then traditional lifting procedures will collect the print.
On certain items that require processing, such as tin products or bottles, the use of cyacnoacrylate ester fuming first will help preserve the print in place. Once the item is removed from the fuming chamber, black or magnetic powder can be used to develop the print, along with various chemicals.
Once you fume your items, there are several chemical agents that will help develop the prints better. A good chemical to use after cyanoacrylate ester fuming is Rhodamine 6g. Place R6G in a dish and place your item in the chemical wash. I find that slightly aggitating the item in the wash will help develop the prints better. Once this process is completed, either allow the item to air dry in a drying cabinet or gently remove wet drops by blotting the item using paper towels. To develop these prints you need to use the alternate light source and orange googles. Photography is always the best method to lift any developing prints. This procedure works great on plastic products like plastic baggies or plastic wrap.
Copyright 2007. Mel R. Bishop All rights reserved.