How should different types of physical evidence, like blood and hair, be collected and packaged at a crime scene?

Here's how to collect and package each exhibit:

a)

• (i) A piece of cloth containing wet blood:
  • Collection: Wear gloves. Use sterile forceps to pick up the cloth.
  • Packaging: Place the cloth in a paper bag or cardboard box to allow it to air dry and prevent mold growth. Do not use plastic, as it traps moisture. Seal and label.
• (ii) Splatter of already dried blood on the wall:
  • Collection: Wear gloves. If the blood is flaky, use a sterile scalpel or razor blade to scrape it into a sterile container. If it's a thin smear, use a sterile cotton swab moistened with distilled water to swab the stain.
  • Packaging: Place scraped samples in a sterile container. Air-dry swabs before placing them in a paper envelope or swab box. Seal and label.
• (iii) Hair on the hand of dead victim:
  • Collection: Wear gloves. Use sterile forceps to pluck or comb the hair, ensuring the root is included if possible. Collect any loose hairs by hand or with tape lifts.
  • Packaging: Place hairs in a paper bindle or small envelope. Seal and label.
• (iv) A knife containing wet blood:
  • Collection: Wear gloves. Handle the knife carefully by the non-bladed, non-bloody parts. Do not wipe or clean it.
  • Packaging: Secure the knife in a sturdy cardboard box to prevent injury and contamination, ensuring the blade is protected. Allow blood to air dry if possible before sealing. Label the box clearly.
• (v) Torn pant and clothes with dried blood:
  • Collection: Wear gloves. Carefully pick up the clothing, avoiding further damage.
  • Packaging: Place each item of clothing separately in a large paper bag or cardboard box. Do not fold or crumple excessively. Seal and label.

b) Factors affecting the ability to obtain a DNA profile include:

• Quantity of DNA: Low amounts of DNA (e.g., from touch DNA, degraded samples) can make profiling difficult.
• Quality of DNA: Degradation due to environmental factors (heat, humidity, UV light, bacteria) can break down DNA, making it unsuitable for analysis.
• Contamination: The presence of DNA from other sources (e.g., investigators, victims, other suspects) can obscure the target DNA profile.
• Inhibitors: Substances like dyes, chemicals, or certain soil components can inhibit the PCR process, preventing DNA amplification.
• Sample type: Some sample types naturally contain less DNA or are more prone to degradation.