How are Fingerprints Left Behind When You Touch Something?

Fans of crime shows know that evidence is everything, and something as unique as a fingerprint is often some of the best evidence to help with catching that bad guy by the end of the episode. The science in these shows is often sketchy, but the one thing they do get right is that wherever you go, whatever you do, you’re leaving fingerprints behind. So, how does it happen?

1. What is a fingerprint?
What is a fingerprint in the first place? A fingerprint is a unique pattern of loops, arches, and whorls that form on your fingertips. The patterns are defined while you’re in the womb when pressure is placed on a particular layer of skin in your fingertips. The pressure crumples up and folds over the skin, creating the characteristic fingerprint designs.

2. Your skin isn’t exactly squeaky-clean.
So, what about the fingerprints you leave behind? You might not be able to feel anything on your fingertips when you touch them, but in fact they’re covered in sweat pores that leave oils behind on the ridges. These oils can collect microscopic debris, turning your fingerprints into stamps of sorts.

3. When you touch something, the oils and collected materials on your fingers are left behind.
Like a stamp, when your oil and dust covered fingertips touch something, they leave behind that residue in the perfect shape of your fingerprints. And since every individual has unique fingerprints, this mark you leave behind unknowingly is a crystal clear sign that says, “I’ve been here!”