Anatomy of a Crime Scene
The ASPCA’s rescue work doesn’t end after we save animals from dire conditions—we also work to ensure that no other animals face the same fate. Our groundbreaking veterinary Forensic Sciences Team investigates animal crime scenes to locate, record and preserve physical evidence in animal-related investigations.
Without physical evidence—including bones, animal, animal remains and even financial records—we couldn’t show the link between the victims, suspects, objects and crime scene, so veterinary forensics is a critical tool in the fight against animal cruelty.
While every crime scene is different, the ASPCA forensic scientists use the following steps to gather evidence:
When our Forensic Sciences team arrives at a crime scene, they assess the situation. They examine what dangers might be present, how to best collect the evidence and whether they need extra specialists or equipment.
Next, the team does a walk-through of the crime scene to provide initial documentation. A scene photographer and scribe (writer) comb the property, carefully and thoroughly documenting the scene’s conditions when investigators arrive.
The lead investigator and evidence collection team follow. They assess how to best collect the physical evidence on-scene, and make note of what areas might be at risk for contamination or destruction during investigation—those should be processed first. All the while, the team takes copious notes.
This could be the most important phase of all. There are four major forms of crime scene documentation: notes, photography, videography and sketches, and they all must be done throughout the investigation. Documentation includes all observations of the scene, actions taken, techniques used, description of evidence located and any other relevant information.
Photographs are the most crucial aspect of scene documentation because they capture an accurate representation of the scene and any evidence. The team takes photos at three levels (overall, mid-range and close-up) to document not only the initial condition of the scene, but also to document any changes made during the investigation. We can never take too many photographs.
As a supplement to photography, we use videography to show the scene in real time and to demonstrate the spatial relationship of objects within the scene.
Sketches, both rough and final, are made of the scene to show the relationship of key items of evidence in relation to each other and the surroundings. They include measurements and descriptions of the items depicted on the sketches.
The team has to conduct a systematic search of each crime scene to ensure they catch all the evidence. Based on the size of the scene and the number of people involved, the team chooses a method, like a grid search or a spiral search.
Collection and Packaging
The purpose of proper evidence collection and packaging is to avoid contamination, damage, or loss of evidence. The principles of this phase largely rely on common sense: always wear gloves, never re-use packaging material, package items separately, and use rigid containers for breakable items.
The specific methods used will depend on the type of evidence being collected. For example, trace evidence should be collected with tweezers or tape and packaged in a small envelope, whereas biological evidence that might be wet should be allowed to air dry before being packaged in paper and kept refrigerated.
Once the evidence has been collected and placed into its proper packaging, the container must be sealed, labeled, and signed to prevent tampering with the evidence. As soon as an item of evidence is collected, it should be entered onto both the evidence log and the chain of custody form, which will eventually show a judge that the evidence being admitted in court is the same as the evidence that was collected on scene.
This phase uses the scientific method to form hypotheses, carry out experiments to test the hypotheses, and draw conclusions from the evidence collection.
The lab testing can involve blood, physical items with blood on them, deceased animals, DNA, bone, tissues and many other things. Blood testing for DNA (to determine individual source, or species), bones (trauma analysis and marrow fat testing), deceased animals for necropsy, insect evidence and plant evidence.
DNA testing and trauma analysis can take days to weeks depending on the case. Once the team has its findings, it reports them to the ASPCA Field Investigator, who then provides the reports to law enforcement and prosecutors for case proceedings such as depositions, pre-trial hearings and trial.