- In this part, the students work individually or in pairs first on the introduction, then on two or three Coach activities for measurements of distances between objects on a few pictures of crime scenes. They learn why it is so important that there are pictures available of crime scenes, and how perspective distortion in the pictures can be overcome such that accurate distance measurements between objects on the picture is possible.
The first activity offers instructions how to do perspective correction and come to correct scaling in the software. In the second and third activities the students have to perform the measurement (and perspective correction) on their own. These activities have some assignments. In the third activity students are asked to find some features of the suspect. From the stride length, an estimate can be made of the suspects length, using the same website as activity 3.3 of Subunit 1. Moreover the footsteps on the picture are rotated to the inside, which may be an indication that the suspect suffers from knock-knees (which happens more in adult women than in men).
- Reasons for photography of a crime scene are a.o.:
- the crime scene cannot stay as it is e.g. when it is in a public place. Then pictures are the only way to retain images of it.
- By walking in the scene evidence may be destroyed
- The pictures can be used for future reference
- The pictures give an unprejudiced image of the scene
- for evidence a picture may be used to do measurements of distances between objects.
Students may come up with the fact that nowadays digital pictures are easy to manipulate. So it is important that they are not manipulated. If this comes up, you can let students look for clues of digital manipulation of the three pictures used in this part. Are the pictures original to their opinion? |