CLPEX Chat Board

In the footwear impression evidence literature, are there articles (published or unpublished) that discuss impressions reflecting slipping, i.e., as the shoe contacted the surface.....some slipping occurs; resulting in the examination of the known impression not overlaying exactly on the questioned. I am looking for articles discussing this topic. I look forward to hearing from those who can assist me in this endeavor.

Thank you.

Jan Seaman Kelly

Your query is addressed extremely well in the second edition of Bill Bodziak's book, Footwear Impression Evidence. You need to review the section on variation and distortion on pp. 362 - 365. The author deals directly with the expectation by some examiners "...that all impressions left by a shoe should always thoroughly superimpose with the test impression later made with that shoe." In my experience this is rarely the case. There are so many dynamics involved in the impression-making process that there is almost always some degree of variation or distortion.

An extreme example involves a person kicking a door in an attempt to gain entry into a building. The questioned impressions nearly always exhibit a marked degree of slippage. There is absolutely no way a test impression prepared in the normal fashion would exactly overlay with the questioned impression. However, this should present no real difficulty for the examiner when he/she considers the dynamics of this example. The slippage would be expected and is certainly explainable, and should not adversely affect the examination.

A more subtle example would be a three-dimensional impression in soft soil. As the heel strikes this substrate, some slippage occurs which causes the soil to be pushed forward into a small mound. As the person continues the step, the shoe simply rolls over this mound and pushes off. The scaled photograph of this impression will be shorter than the test impression. Once again, if you are familiar with the dynamics of this example, you should encounter no real difficulty during the examination.

And, if you're still reading, I'll offer another interesting example from a recent homicide case. There was a questioned footwear impression on the victim's underwear. It consisted of a series of ovals, and the known shoe outsoles were comprised of a series of circles (I believe the shoes were the popular Nike Air Force I). At first glance, one may have been tempted to exclude the shoes very quickly. We produced test impressions on roller transport film but we had some obvious problems with the overlay. We then used cloth as the substrate and again had some concerns with the appearance of the test impressions. We were not seeing the oval appearance at all. We stepped back and thought about the dynamics of the case, and considered that the fabric may have been somewhat taut during the event. We also recognized that the underlying material was skin as opposed to a hard surface. I laid on the floor with a piece of cloth stretched slightly over my thigh, and had a co-worker step on the cloth to produce the impression. The resulting impression now had the same appearance as the questioned. We were not able to individualize the shoe, but could report on the class agreement based on physical size, shape, and outsole design. More importantly, we could now account for the distortion. The examiner of record was able to successfully testify to this.

I apologize for the lengthy reply, but I really wanted to emphasize that complete superimposition of test and questioned impressions rarely occurs. There are a number of factors that contribute to this and, when properly evaluated, should present no real difficulties. Of course, if you can't account for the variances and distortions present, then you must exclude the footwear as the source of the impression(s).

John

Greetings: I definitely teach variation of appearances of independent impressions or images from the source, no matter the source. Each independent touching will produce variations in appearances, there will be no such thing as an exact match, with or without slipping or sliding.

This is expressed dramatically in the CTS footwear test 06-533, with a date due of July 17, 2006, also now published on the Collaborative Testing Services web site, http://www.collaborativetesting.com/reports/2633_MI.pdf .

The inked print standards of the known shoe were made by 'rolling the toe area and heel separately onto paper' for images K1c, and were made by 'having the owner wear the shoe and walk across a sheet of paper' for images K1d, according to the scenario instructions provided with the test. The website for this test, under the Manufacturer's Information, describes these standards as 'the two imprints on K1c were made by rolling the shoe onto paper that was attached to a fingerprinting palm roller'.

An examiner in my lab brought examination quality transparensies of K1c and K1d and the images of K1c and K1d to me for review and consultation, prior to submitting the results of CTS test 06-533. If you have access to the test, note the variations in appearances of K1c to K1d, even though they were made by the same sole. The images of K1c and K1d are extremely clear on my copies. There is very little, if any, indication of slipping or sliding. However, due to the variation in applying and pressing the inked sole to the paper for creating a standard image, without indications of slipping, there is interesting variation in appearances of the arrangement of the detail of the features of the sole.

John V.

Thank you Mr. Black and Mr. Vanderkolk for your comments. I have read...and will definitely re-read Bodziak's book. My question focuses on the possible range of distortion, i.e. where the slippage affects the appearance of the size of the impression (main cause of why overlay is not exact), but the impression still contains clarity in pattern design and shape. Also, the distortion, the range of characteristics one would observe in the impression due to the slippage. From Mr. Black's comments, substrate certainly affects the clarity. Right now, I'm wondering about the distortion range on doors. I recognize counters and substances such as mud...the distortion range may be greater due to the flexible nature of mud or the physical movements involved of someone jumping on top of a counter.
I will pull the last CTS test to look at K1c to study the distortion.
I appreciate the comments and assistance for literature references.

Jan

I need to clarify a mis-statement I made. Regarding Mr. Vanderkolk's statement of variation in the known impressions in the last CTS test, I will go back and visit those photos. My faux paux on using the word "distortion". I have a great deal of experience with rubber stamp exams and I am trying to gain a solid understanding of how much distortion can occur within an impression on a door that has been kicked in...and still contain enough clarity to determine if the Q and K are similar in pattern design, shape, or even size.

thank you for your patience.
Jan