Recent technological advances have allowed for a proliferation of digital images that may be involved in crimes. Using these images as evidence in legal cases like child pornography and masked gunmen can be challenging because usually the faces of the suspects are not visible. To perform personal identification in these images, we propose a biometric trait composed of a group of skin marks including, but not limited to, nevi, lentigines, cherry hemangiomas, and seborrheic keratoses. Due to their biological characteristics, we have grouped these as "Relatively Permanent Pigmented or Vascular Skin Marks," abbreviated as RPPVSM. As statistical study of RPPVSM is essential before investigating their discriminative power, we present in this paper the fundamental statistics of RPPVSM. Back torso images were collected from 144 Caucasian, Asian, and Latino males, and a researcher trained in dermatology manually identified their RPPVSMs. The statistical results show that Caucasians tend to have more RPPVSMs than Asians and Latinos, and over 80 percent of middle to low density RPPVSM patterns are independently and uniformly distributed.