7.5: Crime Scene Processing Methodology

The following crime scene processing methodology is based on your author’s personal experience and on the methodologies that are presented by numerous forensic authors, such as Ross Gardner in his book Practical Crime Scene Processing and Investigation (CRC Press 2019, Chapter 2, pages 79-85), with some modifications.

Process #1: Initial notification and response

Document the time, date and method of the call to service. Gather as many details as possible that are available to determine if specialized equipment or chemicals will be needed for the scene. Select your response route, vehicle staging area, and assembly point for responding crime scene personnel. Upon your arrival at the scene, note the time, weather conditions, including winds, precipitation, temperature, and barometric pressure; odors that may be present; the available ambient lighting at the scene and the need for supplemental lighting. Pay attention to the crime scene perimeter as established by the first responders and make the necessary adjustments.

Process #2: Conduct initial observations and deploy additional resources

The crime scene technician should take immediate control of the crime scene and to clear the area of non-essential personnel. If life-saving efforts are on-going, it is recommended that photographs be taken to document the efforts of the medical responders. This documentation can be useful in fending off litigious actions alleging negligence. The photographs may also be useful to convey alterations to the scene during the medical response. If the victim has been removed from the scene, it is imperative to determine their location and to dispatch a photographer to capture images of the injuries before they are bandaged or wrapped, and to collect their clothing. The crime scene technician should make their initial observations, noting environmental conditions and visible items of evidence. It is important to detect and safeguard perishable or fleeting evidence. This evidence may need to be quickly documented and collected before it is lost or destroyed. If the first responding officer is on the scene, it is best to gather information about the scene as it was first discovered, the personnel who had entered the scene and the role they played within the scene, if any item of evidence had been moved or disturbed from its original position of discovery, and any life-saving efforts that occurred. If witnesses to the crime are present, it is advisable that the crime scene technician ask probative questions that might assist the team with determining the sequence of events or evidence that might have been overlooked. Remember that eye-witness testimony may be incorrect depending on their perspective of the scene. Always allow the scene to dictate the processing based on the training and experience of the technician, and not a pre-conceived theory of what occurred. The technician should look for impression evidence, transfer evidence, perishable evidence, trace evidence and scene conditions (odors, lights on or off, doors and windows open or closed/locked or unlocked, etc.) prior to stepping into the crime scene. This can be done conducting a “sweep” of the area using clean white light from a handheld flashlight at a low, oblique angle to the ground. This will allow small objects of evidence that would ordinarily remain unnoticed to cast a shadow. The shadow will direct the attention of the technician to the evidence. The crime scene technician will determine the scope of the scene, establish the crime scene perimeter(s) have been properly established, consider areas of ingress and egress and determine if additional scene security will be required. The technician will make a determination of the type of equipment that will be needed, and to select an area where your equipment can be staged that is outside of the primary crime scene. The technician will determine at this time if there are technicians or analysts with special abilities (i.e. bloodstain pattern analysis, latent print development, shooting reconstruction, etc.) needed and make the appropriate notifications. It is essential that the technician must don footwear covers, latex gloves, Tyvek suit if needed, and an N-95-type face mask before entering the crime scene. The initial inspection of the crime scene is done without touching or disturbing anything in the scene. The experienced crime scene technician will conduct this walkthrough with their hands behind their backs to make sure nothing is disturbed.

Process #3: The decedent

As the body of a person known to be dead falls under the jurisdiction of the County Coroner’s Office or Medical Examiner’s (ME) Office. The scene should be secured, with only rudimentary photographic documentation conducted prior to the arrival of a representative of the Coroner’s or ME’s Office. Efforts to identify the decedent will assist the Coroner or ME, provided these efforts are non-obtrusive in nature and do not involve rummaging through pockets. The decedent should not be fingerprinted at the scene. This should be accomplished following the autopsy in an effort to preserve what forensic evidence may be present on the hands, fingers or under the fingernails of the decedent. In cases where physical contact appears to have been made between the decedent and the suspect, such as manual strangulation, it is advisable to collect sterile swabs of the neck and arms of the decedent for touch-DNA prior to the arrival of the coroner’s detective, or immediately upon their arrival should their presence be required. Inspect the decedent along with the Coroner’s or ME’s representative once they are on scene. Pay attention to body position, clothing, obvious signs of injury, petechiae and anything unusual or out of the ordinary. Coordinate the removal of the body and establish a time for the autopsy. Whenever possible, the body should remain at the crime scene until it can be documented, and all items of evidence recovered. This, however, is at the discretion of the Coroner’s or ME’s Office representative. It must be remembered that in some states, such as California, it is a misdemeanor to move or disturb the body of a person known to be dead without permission of the Coroner, ME or their appointed representatives. Coordinate with the Coroner or Medical Examiner for the time and date of the autopsy, especially if a representative of the law enforcement agency is required to be in attendance.

Process #4: Photographing the crime scene

The crime scene technician should begin (or continue) photographic documentation of the scene. Following established protocols, the technician should capture overall images (scene establishing), medium view (evidence establishing or relational images, and close-up or evidentiary images. Micro-photography is best captured at the forensic laboratory. The technician should first photograph the entire crime scene without scales and markers prior to the addition of these items. When photographing the exterior of a building, the technician should photograph the exterior corners, sides, entry and exits with identifiers such as street signs, address numbers, building name, etc. When photographing the interior of a building, the technician should photograph rooms from the corners toward the center of the room and from the flat walls toward the opposite wall, taking care to overlap each frame by several feet. The technician should remember to record the floor and ceiling of the room. All items of evidence must be photo-documented prior to their removal or collection. Take care not to photograph items added to the crime scene by the crime scene investigation team (forensic lights, forensic equipment kits, etc.). It is best that these items remain outside of the crime scene until the photographic documentation is completed. If additional evidence is discovered following the use of these tools, the tools should be removed from the area before taking additional photographs. Avoid photographing crime scene personnel in the scene unless it is required to accurately depict the object being photographed or in demonstrating a forensic procedure. Evidentiary images should be taken with the goal to fill the frame with the object parallel and perpendicular to the lens. The use of scales in evidentiary photography should be on the same plane with the top of the object being photographed. Compose the photograph, fill the frame and be aware of the lighting and shadows and what is in the background.

Process #5: Documentation of the crime scene

The entire scene should be documented by the crime scene team in a narrative, sketched, and written form prior to the removal, disturbance or collection of any item. The scene should be described in detail beginning outside of the scene and moving inward towards the center of the scene. The narrative should include the building, room, furniture, fixtures, and all pertinent items of interest. The diagram technician should create a rough sketch of the scene including room dimensions, position and dimension of furniture and all items of evidence. The diagram technician should determine the compass direction of true or magnetic north and indicate on the map that the sketch is not to scale. Outdoor scenes may need to be laid out in a grid pattern or searched utilizing one of the approved methods (grid pattern, line, spiral, etc.) prior to sketching. All items of evidence should be measured in their fixed position prior to being collected. At times it is necessary to move items in order to measure or map a crime scene. For this reason, it is essential that the entirety of the crime scene be photographed, before and after the placement of evidence markers, prior to being measured and sketched.

Process #6: Bloodstain pattern mapping

Mapping, marking, measuring, documenting and presumptive testing of bloodstain patterns should be performed by the crime scene analyst or a technician trained and experienced in bloodstain pattern analysis. The documentation of bloodstain patterns should be conducted following the removal of the body. Bloodstain mapping is generally the last stage of the crime scene processing and should only be conducted by trained personnel using appropriate scales and markers.

Process #7: Conduct the first evaluation

Following the thorough visualization of the crime scene and all pertinent items of evidence contained therein, and following the identification, photographing, documentation and sketching of the crime scene, the crime scene team should gather and review notes and observations before continuing with the crime scene processing.

Process #8: Collection of the evidence

Once all items of evidence have been documented, photographed and sketched, it is now appropriate to begin removing, identifying, inventorying and establishing a chain of custody for the items of evidence being collected. As each item is collected, it should be examined for additional physical evidence. Any additional items discovered when the item was moved should be documented, sketched and photographed. Each object should be handled in accordance with established protocols with consideration for subsequent forensic analysis and processing. Should your agency see fit, it is acceptable to appoint one crime scene member as the Evidence Collection Officer. This person can collect all items of evidence, noting the identity of the original person of discovery for the chain of custody, and process all items into evidence. In this regard, the chain of custody is limited to one or two individuals and only one person is required to testify in preliminary court hearings.

Process #9: Conduct the second evaluation

Following the collection of all known items of evidence, it is now a good time to inspect the crime scene using a forensic light source or ALS for overlooked or evidence such as body fluids, trace fibers, hairs, etc., not detected by white light. Following this, it is an appropriate time to process the crime scene for latent prints. With each new discovery, the technician must repeat the above steps in the processing methodology. The crime scene team (ideally lead by a crime scene analyst or above) should ensure that all areas have been searched and that no areas have been overlooked. Advanced forensic chemical examination techniques (Bluestar, luminol, Amido-black, Coomassie Blue, Hungarian Red, Aqueous Leuco Crystal Violet, etc.) or external ballistic examinations should be considered at this time.

Process #10: Scene periphery

The scene perimeter and outlying areas, which should have been checked during the initial observations, should be thoroughly checked again. Information developed during the processing of the crime scene may lead to additional discoveries peripheral to the crime scene. Additional photographs should be taken of these areas if applicable. If items of evidence are discovered outside of the crime scene perimeter, it may be necessary to establish a secondary crime scene and to process the scene as a separate crime scene but using the same case number.

Process #11: On-scene debriefing of the crime scene team

The on-scene debrief consists of accounting for all technicians, evidence items, and equipment. The team should briefly discuss equipment or procedural problems encountered during the processing of the crime scene, and the need for resupply or procurement. This is a good time to discuss any issues that might be challenged later in court.

Process #12: Securing or releasing the scene

A determination should be made by the appropriate investigative personnel, with consideration to the opinions of the crime scene team and analysts, to either release the crime scene to the responsible custodial authority or to secure it for follow-up examination In suspicious death or homicide scenes, it may be prudent to maintain control over the crime scene until the autopsy, as discoveries during the post mortem examination may require additional speculation of the crime scene. Remember, once the scene is released, it may take a court order to return to the scene.

Process #13: Processing the evidence and report writing

At this time, all items of evidence should be appropriately packaged for long-term storage and placed in approved evidence lockers. Determinations should be made as to the disposition of the items of evidence and whether additional forensic examination is warranted. Chain of custody should be maintained, along with an inventory of all items processed into evidence. Reports, finalized sketches, photographic logs, crime scene entry/exit logs, and crime scene notes should be prepared and collected for review and submission. Equipment should be sterilized and provisioned for the next crime scene call-out.

Process #14: Formal debriefing

A formal debriefing should be held within 48 hours of the processing of the crime scene with the crime scene team, analysts, and detectives to discuss the important aspects of the crime scene investigation. This is a good time also to review protocols and procedures, as well as any concerns regarding the functionality, supply or need of equipment to be used at future crime scenes.

Process #15 – Formal debriefing with the prosector

The one process that often gets overlooked until the case is ready to begin the trial process is the debrief of the forensic documentation, evidence collection, and subsequent analysis of the crime scene and the evidence from the scene with the entity that is prosecuting the case against the suspect. This is often left up to the detective who is assigned as the case agent; however, a full understanding of the crime scene and its evidence is not fully presented to the prosecutor. Your author believes that it is always best to have crime scene personnel, especially those who are trained as analysts, to meet with the prosecutors, and to provide them with the accurate details of the crime scene, its evidence, and documentation.