Broken Glass Evidence in Crimes and Accidents Part 2

Broken glass evidence is a silent witness, offering crucial clues in criminal investigations and accident reconstructions. From the way it shatters to where fragments land, every detail can help piece together what happened. This article, building on Part 1, delves deeper into understanding, documenting, and preserving this vital evidence.

Injuries from Broken Glass: Risks for Victims and First Responders

Broken glass poses significant dangers, not just to victims but also to the first responders on the scene. Understanding these risks is paramount for safety and effective evidence collection.

For First Responders

When annealed glass (standard window glass) breaks under moderate force, large, sharp shards often remain in the opening. These can be incredibly dangerous. Glass overhead is particularly hazardous; if it suddenly dislodges, it can fall like a “razor-sharp dagger.” First responders must exercise extreme caution, positioning themselves away from or to the side of broken glass to prevent serious injuries.

For Victims

Even tempered glass, designed to shatter into small, relatively harmless cubes, can cause severe injuries. These cubes can interlock, forming heavy clumps. For instance, in shower door incidents, large masses of glass falling on a bather can cause more than just superficial cuts.

Conversely, large shards of annealed glass are inherently razor-sharp.

A victim tripping over a window frame with upward-pointing glass can sustain deep, life-threatening lacerations. In such scenarios, rapid action by first responders to control bleeding is critical to prevent fatal outcomes.

How glass enters the human body can itself be significant evidence. The size, position, angle, and shape of lacerations can provide vital information about the victim’s body position both before and during an incident. This underscores the critical importance of taking meticulous, multi-angled photographs of all glass-related injuries.

Documenting the Scene: Photographing Glass Evidence

Thorough and systematic photography is essential when glass is involved in a crime or accident. Law enforcement personnel must prioritize avoiding any disturbance of the evidence. Begin with establishing shots, wide-angle photographs that capture the entire surroundings, providing context for the broken glass. Next, capture the whole piece of glass remaining in the opening from a central point to minimize parallax distortion.

Follow with sequential close-ups taken around the edges of the broken glass. After documenting the glass in the frame, focus on the shards on the floor or ground. Photograph these shards, then lay a tape measure across them and re-photograph.

In one set, place the tape’s tip at the glass face and extend it straight away, showing how far shards traveled – an indicator of the force involved. In another place, the tape is parallel to the frame on the floor. This illustrates the dispersal pattern of the shards, potentially revealing if force was applied at an angle rather than “straight-on.”

Preserving Broken Glass Evidence

Proper preservation is crucial to maintain the integrity of broken glass evidence. If evidence collection is deemed necessary, always collect a few pieces. Store glass in labeled containers that are appropriately sized, preventing the specimens from moving around and breaking further. Crucially, do not store broken glass with fibrous materials like cloth or paper towels.

If blood is present on the glass, it must be collected as evidence, but only after being air-dried first. In cases involving fatalities, serious injuries, or felonies, careful consideration should be given to collecting all broken glass remaining in the frame, as well as any on the floor or other surfaces, with minimal disturbance.

To collect glass still in a window frame, stabilize it by applying 2-inch-wide clear packing tape to one side only. For larger areas, 24-inch-wide clear carpet protection rolls can be used. Once taped, mark the tape with the date and time, add arrows indicating “up” and “down,” and write “inside” on the interior surface. Photograph the glass in the frame with these labels visible and in context.

After stabilization, enlist a glazing contractor for careful removal. Ensure they tape the edges once the glass is out. Finally, cut a piece of plywood to the same size as the glass and tape the broken glass evidence to the plywood. This secures the proof of storage.

An astute detective took these excellent shots of broken storefront glass that gave way easily when a bicyclist pressed against it. We know the glass broke easily because the broken glass evidence included very large shards. This is a classic low energy break. The inset at right shows why the glass gave way so easily. It was already damaged prior to this fatal accident. Someone put tape on the original crack in an effort to hold the glass together. Glass that has been cracked is dangerously weakened. It can be a catastrophic accident waiting to happen. In this case the bicyclist died from his injuries. Photographically these photos show the power of an establishing shot coupled with a closeup.

 

Utilizing Glass Evidence in Investigations

Broken glass can be a powerful tool for placing a suspect at a crime scene and evaluating building safety.

Linking Suspects to the Crime Scene

Glass breakage can be so explosive that tiny shards embed themselves in the clothing of nearby individuals. If a crime involves broken glass, the perpetrator may have such evidence. Given that most of this evidence can be lost within 24 hours, it’s vital to meticulously check suspects’ clothing.

A skilled forensic lab can match glass from a suspect’s clothing with glass from the scene based on color, composition, refractive index, and density. This can link an individual to the incident, such as an intruder breaking into a house.

 

 

Assessing Glass Strength and Liability

Some crimes and accidents involve individuals crashing through window panes. A key question arises: Was the glass sufficiently strong for its application? Certain types of glass, known as safety glass (tempered or laminated), are mandated for specific uses due to their increased strength or breakage characteristics. If the glass was not safety glass where it should have been, the building owner may face liability.

Even when safety glass isn’t required, glass should be strong enough to withstand wind loads. If it’s too thin or weak, an injured party may have recourse against the building owner. When handled correctly and understood thoroughly, glass can be the conclusive evidence that helps close a case.

Challenge Answer: The top impact occurred first. Its primary cracks extended to all glass edges. When the second impact happened, a vertical primary crack from the first impact already existed nearby. As the primary cracks from impact #2 reached this pre-existing crack, they stopped. This demonstrates how primary cracks seek to release impact energy by extending to a glass edge, even if a previous impact created that edge. How did you do?

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