Delayed Entry Apartment Assault: Documentation Under Heat and Contamination
At 14:20 on a July afternoon, patrol requests CSI for a two-bedroom apartment where a 35-year-old woman was assaulted. The rear door shows pry marks. The victim was found in the hallway and moved to a stretcher by two paramedics before the scene was secured. A neighbor entered to check on her and walked from the front door to the kitchen. The scene was not cordoned until 18:30, 4 hours 10 minutes after the call. Ambient temperature is 31°C with 68% relative humidity. Visible evidence includes wet blood droplets in the hallway, a wet blood pool near the kitchen threshold, a dusty shoe impression on dark tile in the kitchen, and a smartphone on the coffee table. One CSI and a trainee have about 6 hours of daylight left. The detective asks you to prioritize documentation and collection and to explain what contamination can and cannot be remedied.
1. What should the first 60 minutes of documentation and processing look like? Justify your sequence using the physical conditions and evidence types.
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First 60 minutes: (1) establish and log an outer perimeter, entry/exit log, and sketch baseline; (2) walk through without disturbing the floor path, photograph overalls from each corner and along the hallway-to-kitchen axis; (3) photograph the dusty shoe impression before anyone crosses it again, using oblique light and a scale; (4) photograph and then collect the wet blood pool and droplets, because 31°C and 68% RH will dry and degrade them; (5) only then process the smartphone. The reasoning is perishability: the dust print is transient and the wet blood is biologically degrading, while the phone is stable and can be swabbed later. Starting with the phone would risk transfer and lose time. Document contaminated paths first so the scene record explains why some areas are not pristine. The trainee should photograph while you collect, but only after the overall sequence is captured.
2. The first responders and neighbor have contaminated the scene. How do you document contamination, and what practical steps reduce further loss or cross-transfer?
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Documentation: scene log entries for each responder and the neighbor-name, agency, time in/out, route, actions, and glove use; photographs and a diagram of their shoe patterns and the victim's movement; notes on disturbed surfaces. Practical steps: define a single entry path, use step plates or paper, change gloves between areas, avoid kneeling in blood, and do not process a contaminated area as if it were pristine. Collect elimination prints or reference samples only if they will help interpret a specific transfer, such as a responder's shoe print; otherwise note the limitation. The key is that contamination cannot be undone, but it can be documented and segregated so the probative value of untouched areas is preserved. If the neighbor walked to the kitchen, treat the kitchen threshold as a contaminated corridor and prioritize the undisturbed hallway droplets.
3. For the wet blood pool on tile and blood droplets on porous grout, what collection decisions do you make and why?
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Wet pool: absorb with sterile gauze or pipette into a sterile tube, air-dry the gauze, refrigerate; do not seal wet in plastic. Droplets on grout: if still wet, absorb; if drying, swab with a sterile swab, air-dry, and package separately. Porous grout may require cutting a section if the stain is concentrated and the surface can be sampled without destroying a pattern; photograph and sketch first. Keep each sample separate, collect a control swab of nearby unstained grout, and note any cleaning chemicals. The judgement is to preserve liquid and absorbed blood for DNA and possible toxicology while avoiding smearing that would destroy the pattern's interpretability. The pool is more voluminous and can be sampled with a pipette; the droplets are small and should not be diluted with water or smeared across the grout.