The risk of Behind Armour Blunt Trauma (BABT) has become a primary concern for the law enforcement officers, soldiers and armour manufacturers. Indeed, the need for body armour weight reduction and the enhancement of projectile efficiency may result in a higher body armour deformation and therefore, an increasing risk of blunt trauma. This study focuses on the soft body armour deformation where blunt trauma is supposed to be mainly due to the dynamic deformation of the protective equipment. Indeed, for the velocity range considered, it is assumed that trauma linked to shock waves may be neglected. The transparent synthetic gel SEBS is employed by the French Ministry of the Interior to capture the dynamic deformation of the body armour and interpret the impact scenario. In order to replicate impact conditions on a biofidelic human torso Finite Element (FE) model, it is necessary to develop a procedure for the modelling of various projectiles and soft body armours. Indeed, the complex material behaviour of the projectile and the body armour during dynamic loading makes difficult the numerical study. Firstly, the experimental backface deformation is exploited to build the geometry of an equivalent rigid projectile. Secondly, an inverse iterative approach using both experimental and numerical model of the gel block leads to the identification of the body armour material model. The maximum backface deflection is used as objectives to reach in the identification procedure, along with the shape of the deformation. This method is validated by comparing experimental tests with different projectiles and body armours with their corresponding FE modelling. Then, the impact conditions are replicated on the torso model and the viscous criterion is calculated. Finally, a previous study about the risk of rib fractures evaluation during the impact of less-lethal kinetic energy projectiles is applied and extended for body armour assessment.