The actions of control, preserve, record, recover, and reconstruct, are the core principles of crime scene examination. They can be remembered using the acronym COPRRR, pronounced “copper,” which, for non-UK participants, is acceptable slang for police officer. The last of these, reconstruct, is somewhat more complex than the others. Control is essentially control of access to the scene. Why is this? If we think back to the quote from Kirk, and the discussion about the Locard Exchange Principal, it should be clear that there is a very real risk that anyone entering the scene may alter it by contamination. Something as simple as an onlooker coughing could contaminate an item with her DNA, and thereby destroy potentially valuable evidence.
Add to the risk of contamination the fact someone not familiar with scene examination may damage it unwittingly by actions such as picking something up for a closer look, leaving a footwear impression over one made by the perpetrator, or turning on a computer. And we can see why being able to control access to those who need to be there is important. The only acceptable circumstances to allow access by anyone other than the active investigators, police and forensic personnel, are those concerning safety. We saw this in the case when the timely presence of the paramedics was critical to saving the life of Mr. Ward. Access control and safety are sometimes obvious.
Public and general busybodies have no legitimate reason to be at a scene. But what if the scene includes access to property not directly involved in the suspected crime, and people want to go home? The answer to that is twofold. The access route to the place where the crime took place is an integral part of the scene. And at the start of the investigation, the ABC principle, accept nothing, believe nobody, and check everything. Dealing with access depends on circumstances. For example, in this case, minimal access control was implemented. The road was the only access to and from the priory. And the primary scene was the car, which could be more safely and effectively examined at the crime scene unit garage.
The last element of control which has to be considered is that the scene of the crime will be governed to some extent by the law and standard operating procedures that apply in the jurisdiction where the suspected crime occurred. These may include procedures regarding admissibility of evidence. For example, there may be requirements regarding what constitutes a legal search and seizure procedure, as in the USA. Americans will be familiar with this.
Clearly access control is important. But identifying the boundaries of the area to be controlled may not be straightforward. Think about the cascade in identifying and managing perimeter control as we move from a house-breaking, to a house and gardens where a murder took place, to a public area where a bomb has exploded. There are no absolute answers. But safety is a particular issue in the last, where buildings may be unsafe. Investigators cannot be sure that there is not an unexploded bomb at the scene. And services may be disrupted.
This was seen in the investigation of the 1993 World Trade Centre bombing in New York when investigators were working in an area in the dark with damage that left holes through five floors, and with ice on the ground from the winter cold, freezing water that had been sprayed on the fire.
For larger and more serious crimes, control is implemented by using cordons. The conflicting needs of absolute control of the scene on the one hand and legitimate access to the area on the other, are dealt with by deploying two cordons where required. An outer cordon with moderate access control is set up at what would seem to be the outer limit of interest. And a tightly the controlled inner cordon is set up around the focal point of the scene.
The final aspect of control to be considered is this. How do we deal with the fact that it is impossible to access a scene without some degree of disturbance? The inevitable disturbance created by the FOA, and, if they were required, emergency services personnel, has to be accepted. But what happens after that can and must be controlled. This is achieved by establishing a common approach path, or CAP. An axis route to the scene that avoids any areas that may have been used by the perpetrator to enter or leave the scene is identified, searched, recorded, and cleared.
To sum up, the main points in control are that access to the scene must be controlled for the purposes of safety and security, integrity, and legality.