Aim:
The aim of this activity is to make you familiar with image-measurement technique and to use image measurement to analyse criminal images, technique used in the professional field of forensic science.
Task:
In this activity you are going to perform measurements on a digital image taken from a crime scene. Follow the original student activity as described in “Measuring on crime-scene pictures activity” (from the unit: Forensic Science, Activity 4)
As a forensic scientist you cannot always walk through the crime scene. This can be due to any number of reasons; you may destroy evidence, or you may be called in at the moment the crime scene has already been cleared away for a long time. In these cases the pictures may be the only way to know what the crime scene did look like. If you need to collect information e.g. about distances between objects, you have only the picture at your disposal. Normally it is impossible to take an overview picture of a crime scene from directly overhead. Therefore we need to consider the significant impact of perspective distortion.
Explain in your own words what you think is meant with perspective distortion? If you do not know, find some information about perspective distortion.
What evidence can you give that there is perspective distortion in the pictures within the activity?
The pictures of a crime scene will be analysed. An important thing to do is determining distances between different objects.
- Give some reasons why it can be important for you as a forensic scientist to know the real distance between objects in a crime scene.
- Find out what is meant by perspective deformation and write a summary in which is explained how this can occur.
Work through the Activity 15-4 worksheet
Resources & Files:
Activity 15-4, Forensic Science, Measurements on crime-scene pictures