||This work deals with the extraction of stress intensity factors in the three dimensional problems. In order to have a good estimation of them, a special class of mixed finite element, named “Metis” element (mongrel element), coupled to a code evaluating overstress, is used. After a brief explanation of the asymptotic model leading to stress/displacement in the vicinity of a delamination crack or a singular line at the junction between different materials, a simple and accurate numerical method is proposed. Next, the singular part is included in Metis element to estimate simultaneously the structural variables and the stress intensity factors. Finally, a numerical example on a bimaterial is illustrated and compared with a case found in the literature.