Movement artefacts distort handheld measurements of laser speckle contrast imaging (LSCI). Enabling a robust LSCI in handheld use brings convenience for both patients and clinical staff. However, there is a lack of a comprehensive model that can predict and potentially compensate the amount of movement artefacts occurring during a handheld LSCI measurement. Here, we propose an analytical-numerical model based on the optical Doppler effect for handheld LSCI in case of translation on a high scattering static surface. The model incorporates the type of illumination as well as the imaging geometry by taking into account the spread of wavevectors for illumination and detection. We validate the theoretical model by simulated dynamic speckles and experiments for the cases of (1) planar and spherical waves illumination and (2) scrambled waves illumination. Results of the speckle simulation are in agreement with predictions of the numerical model for semi-circular form of the density functions of the incoming and outgoing wavevectors.