Even when a person touches an object, “DNA is not always detectable, meaning that it is possible to have someone touch an object but not leave behind detectable DNA because … some people leave more of their skin cells behind than others, i.e., some people are better ‘shedders’ of their DNA than others. There are also other factors that affect the amount of DNA left on an object, such as the length of contact, the roughness or smoothness of the surface, the type of contact, the existence or nonexistence of fluids, such as sweat, and degradation on the object.” Id.,