1. Forensic Science
4.4 Microscopic evidence

2. Learning outcomes
Understand the distinctive features of trace evidence
Know how microscopy can be used in Forensic Science

4. Microscopic evidence Many types of evidence are to small to examine
Standard light microscope – not powerful enough
Need better resolution
Sharper image
Scanning Electron Microscope
Small as 10 nm
20x better than light microscope

5. Better and better Better contrast Improve contrast by:
Clearer image
Improve contrast by:
Staining with coloured dye
Polarising microscope – brightens object
Comparison microscopy
Bullet casings – which gun fired them?
Striations

6. Why’s it useful? Trace evidence can link a person to a place
Paint, pollen, dust, soil
SOCOs use tape or suction to remove samples from clothes and upholstery
Make up of dust is distinctive to certain areas – especially pollen

7. Pollen is the male gamete of flowering plants.

8. Apart from being useful to honey bees, it can be used by forensic scientists to link a suspect to the crime scene where a particular plant may be found growing.

9. Pollen grains come in all shapes and sizes…. …
Pollen grains come in all shapes and sizes… ….and they never decompose! Meaning forensic scientists can identify them on the remains of bodies from 100’s or 1000’s of years ago!

10. Mummy of Queen Hatshepsut

11. These pollen grains come from different species of borage or Forget-me-nots

12. These 2 green pollen grains are sunflower pollen.

13. This is grass pollen

14. This is oriental lily pollen