Forensic Image Sleuth™ tool for the Macintosh

Like the Forensic Audio Sleuth tool, the Forensic Image Sleuth tool was designed for use by Anthony Pellicano of Forensic Audio Labs. The purpose of this 2D image measurement tool is to make precise angular and distance measurements of track and head placement which are encoded on magnetic media like cassette tapes. These measurements aid in the analysis of a tape to determine, for example, if a particular cassette tape was recorded on a particular cassette recorder or if a tape was erased. More details can be found in my resumé. This application was written in C.

 

 

This shows a screen shot of the application. In the Upper left we have a tool bar with a magnifying glass and a grid tool. The upper right shows a scrollable preview of the entire image and below that, various bits of information are editable depending upon the selection. The image shown is a that of a micro-photographed standard cassette tape which has had ferro-fluid applied. The regularly spaced vertical bars show the magnetic force lines present on the tape. The top portion shows a stereo signal present on one side of the tape and the bottom shows a mono signal on the other. Various measurements can be made and the final result can then be exported as a TIFF or printed directly to a color printer

A magnified view of the above shows all measurements are very precise. Usually a micro-photograph is taken of a high resolution caliper reference and placed in an image layer behind the image shown. A calibration step is performed after which distance and angle measurements can be made relative to the two red calipers shown above. In this case there is a slight alignment error of 0.058 degrees at the top of the mono channel. This information can sometimes help link a tape recorder to a tape