Okay, well here you go, since you are in this disbelief humans "shed" their skin. https://skincaregeeks.com/how-long-does-it-take-to-shed-your-skin/#:~:text=Your%20skin%20cells%20are%20held%20together%20by%20desmosomes%2C,is%20between%200.03%20to%200.09%20grams%20every%20hour do you not know basic Biology? Before anyone says "your DNA is not stored in shedded skin cells" (Skin and Hair: Skin cells and hair are other ways in which a criminal may leave DNA evidence at a crime scene. Dead skin cells and hair follicles naturally fall away from the body on a regular basis, and their presence at the crime scene may provide enough information for DNA analysis.") If that wasn't the case they wouldn't be able to track criminals down using it.