Working the Crime Scene: Control, Preserve, Record, Recover

Forensic Laboratories process and report on evidence for the Courts. But how does that evidence arrive from the crime scene to the Laboratory uncompromised? It takes a great deal of skill and care while working the crime scene, in order to maintain evidence integrity.

While working a crime scene, there are four important things to remember in order to effectively collect evidence: Control, Preserve, Record and Recover. In an ideal world they would always occur in that order, but real life gets in the way of perfection. Paramedics need to remove casualties from a scene, fire fighters have to put out the fire: in both cases they are very necessary and there is no way to prevent them from inadvertently damaging any potential evidence to preserve life.

What is a crime scene?

First let’s start with definitions.

Image 1: Definition of a Crime Scene

One definition I found for Crime Scene says that it is a place where an offence has been committed as shown in image 1 above. This is not strictly true; that is a Primary Crime Scene. A crime scene can also include the car that the alleged criminals used to get to the crime scene and the house where they live; these are Secondary Crime Scenes ( Lyle, 2019). A Crime Scene can be any place that is even tangentially related to a crime that has taken place. They are places from which there is evidence to be collected (McMahon, 2022).

Initial Call to the Crime Scene

When the first call to the crime scene occurs, the first person to respond is fairly junior. Their task is to assess whether a crime might have taken place. If their judgment suggests that this is the case, then their job turns into one of control, preventing any further access until such time as more senior investigators arrive. The first person on the scene must take as much care as possible to prevent disturbing any evidence. This may be difficult if they are required to restrain a potential suspect, but should do their best to take notes as to the initial appearance of the site (Schiro).

Controlling the Scene

The importance of controlling the crime scene cannot be understated. If evidence is to be collected, and be able to stand up in court, then entry to the scene must be regulated to prevent cross contamination. Crime scene tape, so beloved of the TV series is one part of the business.

Safety

First of all, the safety of the area must be assessed. Until the scene is safe, the Crime Scene Investigators (CSIs) cannot enter the area to collect evidence. In investigating fire or explosion scenes there is a danger that the building might collapse.

The Cordon

Initially, an area as large as possible should be marked off with tape, and the public prevented from access until such time as it can be cleared. Often the landscape will provide a physical perimeter such as a high fence. If a shop has been robbed, then the street outside might also contain evidence, and should be included in the cordon  (McDermid, 2014). An inner cordon might also be established around the main action of the alleged crime. Once the outer cordon is cleared, then the area under control can be reduced to allow members of the public about their legitimate business (NFCC, 2020).

The Common Approach Path (CAP) into the Scene

Once a cordon is in place, one of the best ways of preventing contamination of the scene is to create a CAP. If everyone walks the same route into the scene then it is less likely that foreign artifacts are introduced to the scene. In order to establish a CAP, the potential route of the path is searched for evidence and cleared before anyone else is permitted to enter the scene. If at all possible the CAP must avoid any entry or exit points used by an alleged criminal (UK.gov ).

Case to Study

In the US, the OJ Simpson Case, where Simpson was alleged to have murdered Nicole Simpson but was acquitted,  is an excellent example of how not to work a Crime Scene. The CSIs failed to set up a proper CAP. Much of the evidence in this case was decreed unusable in a court of law (Crossley).

Locating entry and exit points

Entry and exit points are important because they often contain the best evidence, for instance the fingermarks  on the door handles. One of the best methods of determining the entry and exit points is by talking to witnesses. Observing the scene also works well. If there is only one door or maybe you can see a window is smashed, then common sense suggests checking those points ( Lyle, 2019).

Scene Guard

The role of a scene guard is to allow only essential people access to the site. The scene guard must also keep a scene log of anyone entering or leaving the scene. They also ensure that Personal Protective Equipment (PPE) is worn by all those who are allowed entrance, to prevent contamination. They can also arrange an escort for members of the public who require legitimate access to the scene (NFCC, 2020).

The recurring theme in all of the control measures is preventing contamination of the scene (Schiro). If control is correctly enforced then we can assume that anything found within the cordon might be potential evidence.

Preserve

Once the scene is declared safe and is properly controlled, the next action is to preserve any potential evidence. The prevention of contaminating the scene is also a major part of preservation. As mentioned above, the scene guard prevents anyone from entering the scene without appropriate PPE to prevent cross contamination.

Personal Protective Equipment (PPE)

The full white suit with a hood is a regular sight on the CSI TV shows. The suit, with mask, gloves, booties and hairnet are an important part of preserving any potential evidence. The breath of a CSI or their hair may add extra DNA to the scene. With the modern Polymerase Chain Reaction (PCR) DNA testing, even minuscule amounts of DNA can be identified. Gloves, of course prevent contact DNA as well as fingermarks added to the scene. Wearing the full protective suit prevents fibres from the CSIs clothing from entering the scene. If evidence is to stand up in Court, then all cross contamination must be eliminated (UK.gov).

Stepping plates

If there is only one entry and exit point for your crime scene, how are you to create a CAP?  The answer is Stepping Plates. Everyone must walk into the scene over the plates. If there is a footwear mark on a carpet that might be evidence, place a stepping plate over it to preserve it for the next action: recording (Searching).

Searching the Crime Scene

While some evidence stands out as soon as you arrive on the scene, trace evidence takes some finding. A systematic search must be undertaken.

Search patterns

Image 2: Search patterns.
Credit: Lyle, 2016

A Crime Scene Manager (CSM) must ensure that every piece of potential evidence is located. Practice has found that certain search patterns provide more information.  Image 2 shows a four of these patterns that produce results (Lyle, 2016).  There are others such as the wheel or ray approach that has the CSIs search out in rays from an initial starting point.

Fingertip search

When a crime scene is very defined,  a very close search of the area can be instigated. A fingertip search is not always on hands and knees, it just means an intensive search of the area. You can see an example of searching a crime scene in this video.

Weather

What if your crime scene is outside? And it’s about to rain. Is the evidence likely to be damaged by the weather? Sometimes an attempt to protect the evidence could damage or contaminate it. In this case it might be best to skip on to recovery, but for the most part crime scene tents can protect the evidence so that recording and recovery can proceed in the proper order to ensure the evidence in properly attributed (Baldwin, 2017).

Record

Recording the Crime Scene means more than just photography, although that holds a vital function. The video above in the fingertip search section shows a photographer recording evidence before it is collected.

Photography

As this is the best know method of recording we can start here.

Wide angle shot

A photograph of the whole crime scene is essential, as a reference for later. It also allows any potential evidence to be placed in context of the crime, with evidence markers visible. Where possible the photographs should also tell the narrative of the crime.

Entry and Exit shots

As mentioned above, much potential evidence is located at the points a criminal choses as the entry and exit points (Gouse, 2018).

Evidence

All evidence such as footwear marks, fingermarks, blood patterns and weapons should be photographed with scalers (Staggs, 2014). In Image 3 you can see some potential drug samples next to a scaling ruler.

Image 3: Photograph with scaling ruler
Credit: V.Knipe

Contemporaneous Notes

At the crime scene all personnel should keep notes of that actions. They should be made at the scene or as close to leaving the scene as practical (Forensic Notes). All notes need to be taken in pen, not pencil so they cannot be changed. They needed to be dated and have the time included. Everything, photographs, diagrams, sketches, tapes, all actions should be documented so that if there is any question of what happened in an investigation, then these notes can be checked even if the evidence is subject to a Cold Case Review  (Future Learn (1)).

Recovering the Evidence

Once all the previous steps have been taken, then the process of recovering the evidence can take place. The most important thing to remember is the Chain of Custody or Continuity.

Chain of Custody or Continuity

The Chain of Custody is a paper trail that document every movement of a piece of evidence from the moment it is collected to its presentation in court. Every transfer, every time the evidence packaging is opened for analysis and resealed must be subject to signatures, purpose of transfer, and dates (NIST).

Packaging

It is important to remember to use common sense when packaging an item. A hypodermic needle does not go in a paper or plastic bag, it is transported in a solid jar to prevent injury to anyone in the evidence and analysis chain. A container should not damage any evidence and should be properly labelled and sealed to ensure the Chain of Continuity (Future Learn (2)).

Finally

When working a crime scene it is important to remember that everything collected must be in a condition to provide evidence in a Court of Law. Chain of Custody must be unbroken with every movement traceable or that evidence becomes worthless. Contamination is another issue that can destroy the value of evidence. A CSI must remember to wear PPE and label everything correctly. Then and only then can the evidence be used to help solve crime.

References

Baldwin, H.B, and Pushkarich, C. (2017) Crime Scene Contamination Issues. Crime Scene Investigator Network. https://www.crime-scene-investigator.net/crime-scene-contamination-issues.html

Crossley, J. Common Approach Path. The OJ Simpson Case. http://jamescrossleyblog1999.blogspot.com/p/common-approach-path.html  

Forensic Notes. What are Contemporaneous Notes? https://www.forensicnotes.com/digital-forensics-documentation-contemporaneous-notes-required/#:~:text=What%20are%20Contemporaneous%20Notes%3F,recollection%20of%20what%20you%20witnessed.

Future Learn (1). How to take good forensic notes. Kings College London. https://www.futurelearn.com/info/courses/science-behind-forensic-science/0/steps/56531

Future Learn (2). Evidence Recovery and Collection. Kings College London. https://www.futurelearn.com/info/courses/science-behind-forensic-science/0/steps/56539

Gouse, S., Karnam, S., Girish, H. C., & Murgod, S. (2018). Forensic photography: Prospect through the lens. Journal of forensic dental sciences, 10(1), 2–4. https://doi.org/10.4103/jfo.jfds_2_16

Lyle, D.P. (2016) How Forensic Experts Search a Crime Scene. Forensics for Dummies. https://www.dummies.com/article/academics-the-arts/science/forensics/how-forensics-experts-search-a-crime-scene-138085/

Lyle, D.P. (2019) Forensics: Assessing the Scene of the Crime.  Forensics for Dummies 2^nd Edition.  https://www.dummies.com/article/academics-the-arts/science/forensics/forensics-assessing-the-scene-of-the-crime-200080/

McDermid, V. (2014) Forensics: The Anatomy of Crime. Profile Books Ltd.

McMahon, M. (2022) What is a Crime Scene? My Law Questions. September 22. https://www.mylawquestions.com/what-is-a-crime-scene.htm

NFCC. (2020) Control Measure: Secure the Scene for Investigation. National Fire Chiefs Council. (September 22) https://www.ukfrs.com/guidance/search/secure-scene-investigation#:~:text=Secure%20the%20scene%20to%20ensure,that%20these%20can%20be%20avoided

NIST. Chain of Custody. https://csrc.nist.gov/glossary/term/chain_of_custody

Schiro, G. Protecting the Crime Scene. Crime Scene Investigator’s Network. https://www.crime-scene-investigator.net/evidenc1.html

Searching the Crime Scene. Castle View Forensics. https://www.castleviewuk.com/ch1-searching.html

Staggs, S. (2014) Evidence Photography at the Crime Scene. Crime Scene Investigator Network.  https://www.crime-scene-investigator.net/csp-evidence-photography-at-the-crime-scene.html

UK.gov. The Control and Avoidance of Contamination in Scene Examination Involving DNA Recovery. Forensic Science Regulator. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/915221/FSR_G-206_Issue_2_Final.pdf