NCJ Number
132184
Journal
Journal of Forensic Identification Volume: 41 Issue: 2 Dated: (March/April 1991) Pages: 96-101
Date Published
1991
Length
6 pages
Annotation
A case is reported of an erase head of a submitted recorder that produced perpendicular, parallel, and diagonal lines when stopping and starting in the recorder mode rather than the normally produced magnetic patterns that are either perpendicular or parallel to the tape edge.
Abstract
Following a review of the theory of the erasing process, attention turns to the anomalous example of two audio cassettes and a Realistic Minisette-15 tape recorder submitted to the FBI to determine whether the tapes had been altered and if they had been produced on that particular recorder. No inconsistencies were found in the recorder's transport and electronic systems. A blank tape, placed in the recorder and magnetically developed, revealed the same set of diagonal lines in addition to the vertical and some horizontal lines. The test demonstrated that the erase head had been partially magnetized in this unique diagonal pattern. It is likely that this magnetic anomaly occurred somewhere in the manufacturing process. 6 figures and 10 references