Forensic microscope, in particular for examination of writing

Details Forensic microscope, in particular for examination of writing Forensic microscope, in particular for examination of writing

1999-06-10

2001-05-29

Henry, Jon (Department: 2872)

Optical: systems and elements

Having significant infrared or ultraviolet property

C359S361000, C359S369000, C359S377000, C359S389000

Reexamination Certificate

active

06239904

ABSTRACT:

BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention relates to a forensic microscope, particularly for the examination of writing.
b) Description of the Problems which the Invention Address
A frequent and important question in the forensic sciences is that of the time of origin of a relevant clue. Unfortunately, the methods of dating for forensics, many of which are known from archeology and anthropology, are either insufficiently accurate or are not applicable in general in view of the available stock of clues. Currently, in many laboratories around the world intensive research is under way to develop absolute dating methods. Unfortunately, noteworthy successes are seen only in some areas.
A particular set of problems is posed by assigning a time to documents of all kinds. The time of origin of a document is very often in dispute. Since the area of disputed documents often involves enormous sums, a method for determining the time of origin is especially important. However, there still exists no scientifically acceptable method in this area allowing an absolute dating of written matter. Therefore, the only remaining possibility of achieving results is through indirect methods.
The earliest possible time of origin of a document can be determined by examination of paper, the writing media employed, or printing methods in conjunction with a gathering of references or data. For example, a document produced by a laser printer cannot have originated in the year 1954. However, questioned time periods must often be narrowed down much further, so that the type of dating mentioned above is inadequate. A very common question in such cases is: “What came first?” Either it is presumed that a document has been tampered with or it is claimed that a blank signed sheet of paper has been used in an illegitimate manner. In the event that there is an overlapping or intersecting of writing media, there is a chance that the chronological sequence can be determined.
The Problem of Intersecting Strokes
At first glance, it does not appear particularly difficult to analyze an intersection of writing media. However, when the set of problems is examined more closely, a large number of sometimes insolvable difficulties emerge. A good overview of these problems is contained in G. Poulin, “Establishing the Sequence of Strokes: The State of the Art,”
International Journal of Forensic Document Examiners,
Vol. 2, No. 1, January/March 1996, pp. 16-32, and in Tschopp/Pfefferli, “Die Anwendung des Rasterelektonenmikroskopes in der Urkundenuntersuchung [Application of the Scanning Electron Microscope in Examination of Documents],”
Kriminalistik
2/98, pp. 137-140.
An especially serious problem in many of the methods described is either their limited effectiveness in delivering meaningful results or an unacceptable level of destruction. Once a document has been examined by means of a destructive method, it is normally no longer usable for further examination. In cases where the examination yields no findings, an indispensable piece of evidence may have been lost forever.
There are two basic points of attack:
1. The microtopography of intersecting writing often supplies information about the chronology or sequence of origin.
2. Chemical, mechanical or optical differentiation of writing media offers further indications.
Previous Methods of Examination
Microtopography
The stereo microscope and scanning electron microscope were previously used in image-generating methods for investigation of topography.
The stereo microscope offers the great advantage that it can work in real time, three-dimensionally and in true colors, but is a suitable instrument only in very rare cases because of its low magnification.
The scanning electron microscope has the great advantage of delivering high magnifications and spatial information. Because of the frequent need for vacuum-deposition of specimens, e.g., with gold, this method is considered destructive. A further disadvantage is the elaborate handling and insufficient capability to give true colors.
Writing Media Differentiation
The differentiation of writing media in the examination of intersecting writing was formerly carried out by microscopy in the visible part of the spectrum in order to render visible differences in color in the writing media employed. Various “lift-off” techniques for (destructive) investigation of the sequence of origin were also successfully used.
Other available techniques: Various methods for differentiation of writing media are known. Probably the most exact method is microspectral photometry in which the light of a point on a sample is normally divided into its spectral components and a curve is then obtained for the spectral intensities (useful range between approximately 250 nm and 1000 nm) of a dye. This method has the disadvantage that a graphic presentation can only be achieved at considerable expense and is therefore without significant value for investigation of the complex structures of intersecting writing. Another method is that of fluorescence excitation in the macroscopic area. In this case, fluorescence is excited in the infrared range by different wavelengths in the visible range or fluorescence is excited in the visible range with ultraviolet light. A video camera transmits the images recorded in this way to a display monitor. However, the method is unsuitable for investigation of intersecting writing because it is not possible to display any differentiation in the detail of the microstructure of the overlap or intersection.
SUMMARY OF THE PRIOR ART
At the present time, there is no commercially available system or technique which can deal in a comprehensive manner with the stated problems relating to intersecting writing and which, in addition is consistently nondestructive in addition.
OBJECT OF THE INVENTION
The primary object of the invention is to provide a system which makes it possible to analyze the microtopography of intersecting writing in a nondestructive manner, in real time and in true colors. A need exists for such a system.
SUMMARY OF THE INVENTION
This object is achieved in accordance with the invention by a forensic microscope for examination of writing which comprises a single-channel microscope with stereo viewing by means of synchronized interchange of the illumination angle in front of the microscope objective and/or of the angle of observation following the microscope objective. The invention further includes means for fluorescence excitation in a range of approximately 360 nm+/−40 nm and/or between 400 nm and approximately 590 nm.


REFERENCES:
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patent: 5835264 (1998-11-01), Tandler et al.
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patent: 197 22 726 A1 (1998-01-01), None
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