Yes they are. The whorls and ridges develop uniquely in each person and are not genetically determined. There are a few famous cases in which criminals have been caught by using toeprints. The first was at a Scottish bakery in 1952 when a safe-cracker was identified by the footprints he left in flour. Toeprints were even suggested as biometric data to be included in the now-abandoned UK identity card scheme.