The potentiality of interpreting theD‐meson decay‐dynamics has revealed itself to be strongly dependent on our understanding of the light‐meson sector. The statistics collected by FOCUS is already at a level that manifests parametrization problems for scalar particles. In this paper the first application of theK‐matrixapproach in the charm sector is illustrated and preliminary results on theD+andDsdecays to three pions are shown. © 2003 American Institute of Physics