Impact of a human blood drop on jean fabric: effect of the relative humidity and temperature.

After a bloody crime event, crime scene investigators find different evidence. By interpreting these later, they can reconstruct the crime scene. Blood drops are one of the most common crime scene evidence. To develop reliable models for crime scene reconstruction, it is important to understand all the phenomena related to their formation. 

We investigate the impact dynamics of a drop of whole human blood on jean fabric. The effect of relative humidity, temperature, and the space between the fabric and the substrate are considered by carrying out extensive experiments. For this purpose, we used human blood taken from the same donor. Blood drops had the same volume and the same initial temperature 37 °C. The impact dynamic of the blood drops is recorded through a high-speed camera. 

The results show that the final diameter is more important at low space between jean and substrate and is more important at high impact velocities. Also, with the same impact velocity, the increase in relative humidity leads to an increase in the final diameter. We will present our results by discussing its dynamics and the influence of all the parameters. Further, we will give a correction of an existing experimental model by taking the relative humidity and temperature into account.