Blood on the Porch: Do the Patterns Match the Suspect’s Shoe?

The investigation into the disappearance of Nancy Guthrie has entered a critical evidentiary phase following the media’s discovery of bloodstains on the front porch of the residence after the crime scene was cleared by the Pima County Sheriff’s Office. Recent public attention has focused on a key question:

Does one particular bloodstain pattern on the porch correspond to the pattern of the shoe worn by the individual captured on surveillance video?

This is not a question of opinion even though it is being widely debated across the internet. Instead this is a scientific question. This is a question of pattern transfer, movement, and physics.

Evidence in Question

• Bloodstains located on the porch tile outside Nancy Guthrie’s front door

• Video footage of a suspect walking up to her door

• The suspect’s shoe

Forensic Framework

This analysis is grounded in at least two core principles of bloodstain pattern analysis:

1. Pattern Analysis

A transfer of blood can occur when a something bloody comes in contact with a non-bloody object. Sometimes…SOMETIMES…let me say it again…SOMETIMES…transfer bloodstains leave behind a recognizable pattern that matches something related to a blood letting event. Not every time. Probably not even most of the time. In footwear impressions, tread design, wear characteristics, or partial sole geometry may be present. Qualified experts are appropriate to render opinions in such cases.

But there are several passive bloodstains on the porch. There appears to be an area of tile that could be consistent with what is often referred to as “blood-into-blood” as well. What is not observable are bloodstains that suggest a beating, shooting, struggle, for example.

2. Substrate Interaction

Substrate is a fancy word for target surface. Target surface is a fancy phrase for, “On what kind of surface is the blood stain?” The porch is made of tile in this case. So the substrate or target surface is tile. It appears to me to be hard and non-porous in the photos and video even though it also appears to be possibly made of clay, which of course is porous in general. So much so that if someone were to Bluestar the tile even after the blood is washed away, they still might see the pattern of where the stains once were due to the blood still adhering to the tile or being partially absorbed by the tile itself. Regardless, target surface, and in this case the tile, plays a critical role in what is observable.

Observed Pattern Behavior

Based on available imagery and footage (remember everyone’s brains interpret shapes differently. One person sees a horse in the clouds another person sees a spider kind of thing.). For me at this point, the porch bloodstains appear disrupted rather than cleanly transferred. I don’t see a clear sole impression preserved in blood. At this stage, the evidence supports the following:

What the Evidence CAN Support

• A person moved through an area where blood was deposited on the porch

• There may be partial transfer consistent with footwear contact…we don’t know

• The scene on the porch reflects standing or slow movement type of activity

What the Evidence CANNOT Yet Support

• A definitive match to a specific shoe

• Individualization to the suspect seen in the video

• A clean, court-defensible footwear impression comparison

…and that’s just for starters. This is where things often go wrong sending people on wild goose chases when being ultra-conservative is best practice: similarity is not identification. A pattern that “looks like” a shoe is not the same as a pattern that can be forensically matched to that shoe. That’s a job for the experts. But this evidence raises important questions:

• Where did the blood originate relative to the porch?

• Was the movement purposeful, hurried, or staged? I don’t think it was staged just for the record, but being objective, fair, and impartial means we consider alternatives until they can be ruled out substantiated by actual evidence.

• Is the blood a transfer? If so where did the shoe come in contact with enough blood to create that pattern?

Bottom line…the blood on the porch indicates movement through an area. It does not yet establish a definitive link to a specific shoe worn by the specific suspect in the video. Evidence must be interpreted within scientific and ethical limitations, not pushed beyond them.