Imagine a detective using a special kind of instrument to see the lingering leftover of magic spell at the scene, markings such as spell circle could help to identify type and nature of the spell used and the damage to the surrounding hints the magnitude and strength of magic casted. It would be more efficient if magic is unique to individual much like DNA, however I dislike borrowing the concept of chromosome because it is too complicated and redundant.
Question: how can I make each spell unique to their caster but still base on a single magic system? For example the detective and use the finding to trace a certain individual but I don't want to duplicate the DNA to use for magic it's redundant and messy.