The tearing energy of a ductile thin plate has long been considered as a material constant. This concept of energy is regarded useful for design of energy absorption components. However, it has been noticed that various existing test data for the tearing energy are not consistent. This indicates that the tearing energy may not be a constant determined by material only. Other factors, such as loading mechanisms and geometry may be influential. In the present study, we propose a ''mode'' concept for in-plane tearing tests by introducing a mixity parameter , for in-plane tearing. Through the finite element modelling, the mixity parameter is calculated from the principal stresses in front of tear tips. Laboratory tests were also conducted on samples with two different geometric configurations. The first set of the tests, conducted on the double-notch-tensile specimen, provided the tearing energy, while the second set of tests on the unnotched uni-axial tensile specimen served the purpose of verification.