The first responding officer will provide a lot of information on what was found upon arrival, what has been touched, moved or removed. The next step is to walk through the scene to get an idea of the nature of the crime, how it was committed, and point of entry and point of exit. The purpose of the walk through is to determine what needs to be more closely examined and what evidence may be present. Once the safest route for traveling through the scene has been determined, it then is time to take photos of the scene.
Photos begin with the general to the specific, a picture of the parking area may be the starting point, with shots of exterior walk ways leading to the scene following. All entry point to the scene need be photographed concentrating on the suspected point of entry. The exterior shots should present a travelogue of how access to this scene was had. Once the exterior shots have been completed the interior shots begin. Room entryways, layouts points of access, contents and furnishing provide a panorama of the interior and will tell part of the story to the jury of what took place and in what order it happened.
Once the general pictures have been taken, pictures of evidentiary items are next. All photos are taken ninety degrees to the surface of the object being photographed. All evidence should be photographed in place as found first and later with evidentiary markers and if necessary something to assist in determining the size of the object such as a ruler, pen or even a coin. A photographic log is kept identifying each picture and the sequence in which it was taken. Once all photos have been taken, they then measure and start sketching. Every evidentiary item must be geographically located, measured and sketched in a field drawing.
The final steps involve the handling and packaging of all evidence, each piece comes into evidence at a specific time. That time begins the chain of custody of that piece of evidence. Police are responsible for accounting for each piece of evidence that comes into their possession. The evidence will find its way to the laboratory or the evidence room where further entries are made to maintain the chain of custody. So to break it down, the steps in processing a crime scene are, securing the scene, conducting interviews, examining the scene, pictures taken of the scene, and finally bagging, and tagging the items found at the scene.
There are five methods in recovering evidence. The first method is called the wheel method; you must begin in the middle of the scene, pick a landmark and walk in a direct line searching the area right in front of you. When landmark has been reached turn and walk back the way you came back to the starting point, at the starting point chose another point to walk and repeat the same method until you have gone in a complete circle.
The second method is called the spiral method; staring the search in a selected point at the edge of the scene, walk in a circular pattern to the center of the scene with the circle getting smaller as you approach the center. This search method is effective in smaller areas. Third method is the strip method; this search is started in the southeast corner of the area. Walk north in a straight line, keeping parallel with the east edge until reaching the north edge of the scene. Then take two steps west and walk south in a line parallel to the first path until reaching the south edge of the scene.
Process is repeated until reaching the west edge of the scene. This method is worked well in a large area. The fourth method is the point to point method which works well in small confined areas, in this method you must go to first piece of evidence, process it then go to the next piece of evidence. This process is repeated until all evidence has been processed and collected. Finally the fifth method is called the zone method and is worked well in larger areas, in this method; the scene must be divided to search in quadrants. Another person may be used, or the investigator can perform the search independently.
Lastly, handling infected evidence in a crime scene. It is very important to get information on the crime scene before handling any evidence, not only that but everyone entering the crime scene must be fully covered so that is evidence is infected, they are sure not to catch it by touching dry blood or anything else that can possibly spread the infection. If in case the infected evidence has been touched by anyone in the crime scene it is a great idea to seek help right away. To pick up any evidence it must be done so with a lot of care.