An apparatus and method for triaging patients according to radiation exposure measures electron paramagnetic resonance spectra of fingernails, toenails, and/or teeth. In vivo, radiation induced spectra are obtained from intact fingernails, toenails, or teeth placed within a magnet and with pickup coils over nails between the cut edge at the end of the fingernail and proximal skin or placed adjacent to at least one tooth. The system may also operate in vitro with fingernail clippings. At least three spectra are obtained with one after a delay at above twenty degrees Celsius, and at least one at power levels different from the others. The spectra are used to determine and remove a mechanically induced signal from EPR spectra to determine radiation-induced spectra. The radiation induced spectra are used to determine radiation dose, the dose is compared to triage limits, and a radiological triage tag is printed for the patients.