A method and apparatus for dating a body sample, for example a sample of body fluid involves taking a series of spectroscopic measurements of the sample, each measurement in the series including at least two predetermined positions in the spectrum. The positions have spectral characteristics corresponding to two or more predetermined substances present in the sample that have a time varying relationship with each other. The measurements in the series are spaced in time. A concentration of each of the substances present in the sample is then determined from each of the spectroscopic measurements at each point in time. Next, a ratio of the concentrations of the two predetermined substances at each point in time is determined and then the ratios of the concentrations of the two predetermined substances over time are analyzed to estimate when the concentrations of the two substances were at a limit of their concentrations, thereby providing an indication of the age of the sample. The sample may be blood, which may be either within the body (e.g. as a bruise), or external to the body.
