"touch DNA" is very difficult to collect and identify. Simply touching something does not necessarily leave behind enough genetic material to identify the DNA of who touched the object. George Zimmerman's DNA was also unable to be identified from the grip of the gun. The DNA tech collected an actual blood sample from the gun grip, but could not positively identify either GZ or TM DNA in the sample collected. The claim that because Martin's DNA was not identified on the gun, he could not have grabbed for it as Zimmerman claims, is a misleading presentation of the science of DNA .