There seems to be no published record of another success with the exclusion of the Turner painting, which is surprising as criminals are sent to jail or even executed based on such evidence. Notwithstanding, paintings and other works of art frequently preserve the marks of the hands and fingers that created them. We seem to take our hands for granted and forget that every time we touch something we leave behind a unique mark. So too do artists working with paints, inks and dyes among the myriad substances used in their creations. These substances may require from hours to days, some even weeks to dry. During this time they are often handled and sometimes carelessly. If an impression is left the dry surface will preserve the print even for hundreds of years. 

Artists in the area of the visual arts use their hands for creation. Their tools, such as brushes often isolate them from the surface they are working on. Inaccurate deposits of paint are often corrected by modeling with the fingertip. Some artists used the fingertip to soften the marks left by the brush by gently tapping or stroking the still wet surface. In some instances, the fingertip was used for literally 'stamping' the fine network of ridges onto the painting. This was done after some suitable color was picked up from the palette. Artists often varnished their own paintings and were not likely to leave such an important process to assistants, creating another opportunity to leave identifiable marks behind. In the 16^th century, for example, various oils have been used for varnish. The oil was spread over the painting by hand and meticulously rubbed into the surface. The contacting surface of the hand was usually the ulnar and hypothener zones preserving a good portion of the palm. A rare example of entire preserved hand prints is found in the Vatican Stanze on Raphael's School of Athens fresco. It appears, that while working on the fresh surface, the artist and/or assistants negotiating the planks on the scaffolding braced themselves against the wall for balance. This intentional or accidental use of the hands gives the perfect opportunity for using fingerprints in identifying an artist. 

If usable prints are found on the work of art under investigation an acceptable speculation for an attribution is attempted. To test the attribution reference material is needed. Visits to museums and collections may be required and the paintings have to be examined up close with a magnifying glass and proper illumination. Eventually, if usable prints are found, they are photographed employing accepted practice. Comparisons can then be made. If a match is found, the attribution can be confirmed under some caveats. Strict logic is essential in estimating the value of a match. The possibility of a hand other than the artist has to be considered and investigated. 

Historical evidence may be essential in this regard and other reference prints may be needed for confirmation. Correct reasoning should consider probabilities such as the likelihood of an assistant being present and contributing at different dates and possibly different locations. An example would be a fingerprint from a Raphael panel painted in Florence and another from his Roman period. In Florence he worked alone, in Rome he employed a small army. If a match were found in both references, it would strongly suggest that the contributor of the evidence was Raphael. When other such matches are found, the probability increases.

Another interesting prospect may occur when two sets of prints are compared from two attributions to the same unidentified artist. If the possibility of two contributors having the same print is nil, then the two paintings can mutually and reciprocally confirm the authorship of the other - whoever the artist may be. When such forensic techniques are accepted and adopted by the art community, many new attributions may be formed, old ones changed and doubtful ones may be resolved. 

Fingerprint evidence can establish dating when no other scientific technique may help. An example is a match established between a fingerprint on a painting that has been argued to be from the 19th century. A match has been made to a print from a 16th century painting, an altarpiece,  whose authorship and dating has never been questioned, it has indeed hung in the same city for the past 400 or so years. The match does not rigorously identify the painter, however, in the least it does date the questioned painting to the lifetime of the 16th century contributor.

It must be stressed again, a match in the above cases does not 'prove' authorship in the rigorous sense of the meaning of the word proof. It does, however, offer valuable circumstantial evidence that can complement a scholar's or experts assessment of a work of art.
 
 

Special Considerations: The Quality of the Data

Both evidence and reference samples are often partial. On an artwork, damage may have been sustained by abrasion or by previous cleanings. The print may be found in conjunction with disruptive or disturbing background upon which it appears. The photographic process, which is often the first step, should be planned to make the most of the sample. If for example, the print is a plastic impression, it would show in relief and raking-light illumination will often enhance such details. Sometimes, the print is in one color over another and this may be used to advantage by employing filters to enhance the contrast. 

Still, the resulting photos may not be very helpful despite all best efforts. Unfortunately, often traditional methods are not sufficient to resolve the problem. Digital image processing of data is now used in many areas of science and technology and this includes fingerprint science. A dedicated and advanced image processing platform can perform hundreds of mathematical techniques on a digital image to help better visualize the evidence. Moreover, an experienced technician can design the appropriate methodology to bring out the most of the relevant data from an image. 

 The image on the left is a detail from Raphael's Mond Altarpiece in the National Gallery, London. The brushstrokes mask the palmprint on the painting making interpretation of ridges extremely difficult. On the right, the brushstrokes are digitally removed making visualization a snap. The bean shaped area in center left is later restoration.

Permission from the Curator of Italian Renaissance Paintings ( National Gallery, London) to examine and photograph this painting is gratefully acknowledged.
 

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A Current Project Involving Fingerprints

In 1998, three envelopes containing old correspondence had been purchased in an antique shop. One of the envelopes postmarked April 2, 1915 was found to contain a drawing folded in half. The drawing depicts a woman's head. It is executed in red chalk with an inscription written in reverse with brown ink. The design is faded and worn. Some spots suggest foxing and subsequent discoloration. The paper is yellowed and contaminated. 

The newly discovered design bears great similarity to that of the Head of St Anne (1) by Leonardo da Vinci, (RL 12533) in the Windsor Collection since 1629. The medium is different, red chalk being used instead of black. The scale of the two images is different so offsetting (copying by contact transference) is not a satisfactory explanation for the new drawing. Differences also exist in the design itself, principally in the folds of the veil, in the presence of an additional strand of braid and in the angle of the head. The figure is softer, which may be due to fading, wear and contamination. In addition, the use of a damp brush is indicated in microscopic examination and is likely responsible in part for the softness of the image. When the paper was first examined, several fingerprints have been noticed on the verso. One of them was found clear and containing many ridges suitable for comparison, however, no analysis was done at the time due to the lack of reference material. Many of Leonardo's works are not easily accessible and fingerprint data either does not exist or is not published. 

By chance, on March 30, 1999, several clear and useable fingerprints were found on an unusually good detail photo in a publication (2) on Leonardo. The photograph of Leonardo's St Jerome, in the Vatican Museum, revealed no less than 16 partial fingertip marks. The importance of this is that the fingerprints are left in the still wet paint and without doubt the use of the fingertip served to model paint. Since the authorship of the painting of St Jerome is unquestioned by scholarship and has always been ascribed to Leonardo, the conclusion that these fingerprints are his would be hard to argue against. 

The fingerprints on the St Jerome illustration were scanned and enlarged so comparisons could be made with the fingerprint on the newly discovered drawing. One of them proved to match. The result of our analyses was presented on March 31, 1999 to fingerprint examiner Staff Sergeant André Turcotte for an independent assessment. He agreed with the findings and confirmed the conclusion. The fingerprint on the St Jerome painting in the Vatican and the newly discovered drawing were created by the same finger. 

The matching fingerprint is powerful circumstantial evidence. It dates the drawing to Leonardo's lifetime and it proves that Leonardo had to have physically handled the paper. Combined with the artistic quality of the drawing Leonardo's involvement past the mere handling of the paper is indicated.

Partial fingerprint 'A' is compared with partial fingerprint 'B'. Both fingerprints appear as being made by the same finger. 'A' is a fingerprint from the verso of the newly discovered version of St Anne. 'B' is a fingerprint from Leonardo's St Jerome in the Vatican Museum. The principal characteristics are: 
1 island, 2 larger island, 3 island, 4 island, 5 ridge ending, 6 ridge
ending, 7, island, 8 lake, 9 very large island. 

The kind assistance of  Staff Sergeant André Turcotte (retired) RCMP is gratefully acknowledged.

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E-mail: artsleuth@sympatico.ca