On the blank paper, ask students to draw around their hand(s). They will add a fingerprint to each of their fingers.
Use the pencil to scribble a dark patch on the corner of the paper.
Rub a finger tip in the pencil patch, pressing it down and rolling it around to make sure the entire finger tip gets coated in graphite.
Stick a piece of tape on the darkened finger tip, then peel it off. Stick the tape on the card over the appropriate finger tip.
Use an identification sheet to first determine whether each of the fingers have loops, arches or whorls. You may also find more complex patterns such as double loops or other combinations. This pattern is caused by ridges of skin. They stay in this pattern throughout your life, and even if you damage your finger they will grow back in the same pattern. Everyone, even identical twins, has a unique collection of fingerprint patterns.
Then look for minutiae - the places where the ridges start and stop and fork and merge. Challenge students to find a bifurcation, lake or hook.
Ask them to work with the magnifier and a fine-tipped sharpie to circle the minutiae that they find, just as a forensic scientist does.
Try these websites for images of fingerprint patterns and minutiae (or google search for "fingerprint patterns" or "fingerprint minutiae"):