The correct information, including the full braking deceleration of a vehicle, is an essential factor of the road accident process analysis. The aim of the paper was to define and compare the braking properties of the tested Tesla model S electric vehicle by means of the XL MeterTM Pro decelograph and a smartphone as a new alternative method. The measured procedure was the intensive vehicle braking by means of a fully pressed-down operation brake from the different initial velocities. Altogether, 32 measurements were carried out, out of which 16 on the dry surface and 16 on the wet surface. This paper contains the methodology and the results of the performed measurements. The data obtained by an XL Meter TM Pro measuring device were processed by means of the XL Visionä and PC Crash 11.0. software, whereas the data from the smartphone was analysed using the Diagram software. The results and data processed herewith can be useful for the forensic practice.