Gazette - First on the scene

FEATURED SUBMISSION

Tips for keeping evidence intact

Cpl Pat Gould
Forensic Identification Specialist
Moncton RCMP

A police officer can expect to attend any number of crime scenes, from simple break and enters to complex homicides. When an officer is the first to arrive on the scene, his or her approach and subsequent actions can make the difference between a conviction or an acquittal in court. This article offers some guidelines for first responding officers on what should be done at a crime scene to reduce the possibility of losing or destroying evidence, or having it ruled inadmissible in court.

First things first

Cpl Pat Gould, RCMP
Fingerprints recovered from broken glass.

When notified of a crime scene, make sure to record any pertinent information such as who made the call and what was said; the date, time and weather conditions; the circumstances of the complaint; and the location of the incident. This information will help you prepare for your response.

Upon arrival, record the time, date, location, persons present, weather conditions and other information from your own observations. Comprehensive notes will be helpful for subsequently providing information to investigators, forensic identification specialists and others, as well as writing reports and testifying.

When first approaching the crime scene, make continuous observations and pay attention to details. For instance, make note of whether the driveway leading to a residence is paved, dirt or snow-covered. Take care to avoid destroying tire or footwear impressions that may have been left behind. Note environmental conditions: a windy day could blow a door closed or move evidence in a yard.

Conducting a preliminary visual examination of the exterior of the crime scene is particularly important as it can uncover many types of evidence such as footwear impressions, tire impressions, cigarette butts and tools.

Securing the scene

Prior to examination by a forensic identification specialist (FIS), traffic into and through a serious crime scene should be limited to those who must enter to ensure officer and public safety. When it is necessary to enter the scene, make every effort to determine the path of contamination, which is the path taken by the offender(s) to, from and through the crime scene. Once the path has been identified, avoid travelling on or crossing it in order to reduce the chance of destroying or contaminating evidence. If a perimeter is required, cordon off a large enough area to prevent loss of evidence, and permit only essential personnel to enter the scene.

To assist in determining the path of contamination once the scene has been secured — if it is necessary to travel in the scene prior to the arrival of an FIS — the first responding officer may darken the room and use oblique or low-angle lighting (45-degree angle or lower) with a flashlight to look for possible footwear impressions. These impressions should be protected until the FIS arrives and is able to examine and process the evidence.

For an FIS, the point of entry yields the best physical evidence, such as fingerprints; traces of hair, fibre or DNA; footwear impressions; or tool markings. Protect the point of entry and avoid using it to enter or exit the scene until it has been examined by the FIS.

If the home or business owner is available, enquire about the last time the windows and floor at the point of entry were washed. This information is very important to establish a possible time frame for any footwear impressions or fingerprints. Also ask the home or business owner if any items have been handled or removed by the culprit(s).

Protecting evidence

Any physical evidence that you observe must be protected from possible environmental conditions — such as rain, snow or sun — and kept intact until the FIS can photograph and examine the evidence.

Cpl Pat Gould, RCMP
This footwear impression was left behind on a cushion at the point of entry.

In adverse weather conditions, the best practice is to place a clean covering such as a cardboard box over the physical evidence. However, this type of covering may not work for footwear or tire impressions in snow. If the sun is strong, placing a box over impressions in snow can create too much heat and actually melt the evidence. Instead, try creating a shadow over the evidence to limit sunlight. For footwear or tire impressions in muddy, rainy conditions, cover the impressions and try to limit water draining into the evidence.

Avoid handling any evidence unless absolutely necessary. If a piece of broken glass with a suspected blood stain is being exposed to rain or snow, you may have no choice but to move that evidence, as it might be the only link to the perpetrator. Wear protective gloves when handling any exhibits, and always notify the FIS of your actions when he or she arrives at the scene.

Never allow eating, drinking or smoking inside the crime scene.

Preventing contamination

Contamination is the altering of the scene or any evidence before the evidence has been recorded and collected. There are few ways in which a crime scene can become contaminated. Witnesses, ambulance attendants and other civilian personnel may similarly disturb the scene. Police officers entering and securing the scene may also cause contamination.

Investigators who leave the scene to deal with a suspect then return following that contact may inadvertently bring contamination or something that could be perceived as evidence into the crime scene. This could lead to an incorrect interpretation of the scene. Similarly, evidence from the scene could be transferred to a police vehicle or interview room. For these reasons, the investigator dealing with the scene should not be the same member who deals with suspects.

Trace evidence such as hair and fibres can also be transferred from person to person when police use the same cell to house suspects or the same vehicle to transport prisoners or witnesses. Although such situations may be unavoidable and cross-contamination is highly unlikely, it is important to show the court that all reasonable precautions were taken.

Gathering fingerprints

Cpl Pat Gould, RCMP
Some surfaces, such as paper and polished metals, are more amenable to retrieving fingerprint evidence than others. These fingerprints were developed on the exterior of a car door.

Police officers should be generally knowledgeable about the kinds of surfaces that are amenable to retrieving fingerprint evidence. Surfaces like glass, plastic bags, paper and polished metals are usually good surfaces. Fingerprint evidence on rough or dirty surfaces may be limited, but FIS members may have other techniques that can be used.

Consult the FIS before making any decision that a particular item or surface may or may not yield the possibility of fingerprint evidence.

Seizing evidence

If the investigator determines that an FIS is not required at the crime scene, items can be seized for future examination. When seizing evidence, it is very important for the investigator to wear proper protective gloves and handle all exhibits by the edges with as little contact as possible. Take detailed notes for each exhibit seized, including the date, time and location of seizure, the file number and the seizing member’s initials.

Secure seized exhibits in a manner that limits friction and the possible destruction of fingerprint or DNA evidence. For instance, avoid placing a bottle to be examined for fingerprint evidence in a plastic bag.

When wet exhibits are seized (excluding fire debris), air dry the exhibits immediately in a secure location to prevent mold and mildew from forming. This includes clothing and footwear exhibits. If clothing and footwear must be seized from the suspect and the FIS is not present, photograph the suspect wearing the clothing and footwear prior to removal. Finally, note any changes to exhibits, such as spillage, seepage and mold.

By following these guidelines, police officers can limit the potential for damaging evidence or contaminating a crime scene, thus increasing the possibility of a successful investigation.

With assistance from RCMP Forensic Identification Operations Support Services.