The largest and best look-alike ever recorded displaying non-pattern force corresponding ridge formations was determined to be that found by John “Dusty” Clark as a result of a California Department of Justice AFIS search [26].  Based on conservative interpretation of quantitative weights, conservative assessment of quality of agreement, and relevant fingerprint population of 65,200,000 [33], the T-Value was estimated to be 417,567,111 and the subsequent number of look-alikes was estimated to be 4.34.  

"Found on an AFIS search, the below images have eight details in sequence that are not from a common source.  This example is numerically the most level two characteristics found in agreement, as well as being the closest in tolerance of spatial relationship that this author is aware of that are not from the same source." 

                                                                                John "Dusty" Clark

    Close-up of Clark latent impression               Close-up of Clark exemplar impression

 Overview of Clark latent v. exemplar fingerprint impressions 

Click here for a PDF summary of the Clark Non-match.

The values for the above pairs of corresponding latent v. exemplar ridge features were multiplied against each other in order to obtain the aggregate total value, e.g., T-Value, as follows:

20 x 52.25 x 1 x 13.375 x 11 x 14.25 x 7.125 x 26.75 = 417,567,111

Based on an estimated California Department of Justice AFIS fingerprint database of population of approximately 65,200,000 (at the time of the find), the number of fingerprint parts (P) and the estimated number of look-alikes (L) is calculated by T-Model formula as follows:

T^P = F

(417,567,111) ^ (P) = 10^120

Log (417,567,111) ^ (P) = Log 10^120

(P) x (Log 417,567,111) = Log 10^120

P (8.62) = 120

P = 120 / 8.70

P = 13.79

L = (R) (P) / T
L = (65,200,000) (13.79) / 417,567,111

L = 2.15

The T-Model calculates the conservative, e.g., upper-bound, number of look-alikes likely to occur in a relevant population group of 65.2 million fingerprints as 2.15. 

As a result, the T-Model correctly identified the amount of corresponding ridge features present in the Clark Non-Match as insufficient to infer positive identification.

Based on a relevant fingerprint population of 65,200,000, a conservative T-Value of 417,567,111, and an estimated number of look-alikes of 2.15, the Clark Non-Match is considered pound-for-pound the largest and best friction ridge look-alike ever seen. 

The following statement by Christophe Champod supports the theory that the Clark non-match is currently the largest and best fingerprint look-alike ever recorded:

“To my knowledge, the most convincing example [of the largest extent of correspondence involving a non-match] has been published by Dusty Clark who reports the following:  “found on an AFIS search, the below images have eight details in sequence that are not from a common source.  This example is numerically the most level two characteristics found in agreement, as well as being the closet in tolerance of spatial relationship that this author is aware of that are not from the same source.” [102]

Christophe Champod

Report to the Fingerprint Inquiry

September 28, 2009
 

NEXT PAGE >>> 

Latent print examiners may use the T-Model Fingerprint Calculator to test and experiment with different arrangements of corresponding ridge features found in any latent v. exemplar fingerprint impressions. 

Any probabilistic model used to estimate numbers of friction ridge look-alikes must be able to reliably identify the largest and best friction ridge look-alikes that AFIS can find in its database as insufficient to infer positive identification.