I present a statistical model for the quantitative peak information obtained from an electropherogram of a forensic DNA sample. The model directly describes peak height information and the dropout of an allele is interpreted as failure for its associated peak to be observed above a detection threshold. Stutter and dropin are readily represented in the model. The parameters of the model, and their standard errors, are estimated by maximum likelihood in the presence of multiple unknown contributors, exploiting a Bayesian network representation for efficient computation. Data from a (murder) case taken from the literature is used to illustrate the efficacy of the model. (This is joint work with: T. Graversen, S. L. Lauritzen and J. Mortera)