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Author Topic: Help on manufacturing marks conclusion: "machine" vs "source" ?  (Read 14066 times)

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Offline Joel

  • AFTE Friend
  • Posts: 1
Hi Everyone,

Greetings from Singapore!

I'm looking for some advice on terms used in conclusions for manufacturing marks on plastics (in particular plastic bags produced by blown extrusion).

Assuming some plastic bags were found to have similar striation marks produced during extrusion at the die, would it be more appropriate to conclude:

1. "The bags were manufactured from the same "machine", or

2. "The bags were manufactured from the same "source"

Listed below are the delimmas I'm currently facing with the above conclusions:

1. The use of the word "machine" implies that the configuration of the machine (Hopper, Extruder, Die, rollers) at the time of production contributes to the striations, which i'm unable to derive based solely on the striae observed.

However, looking at the bigger picture, if we include the shape, size, weight and other physical characteristics along with the striations on the bags, would it be appropriate to use "machine" in that case?

2. The use of the word "source" is more general and implies that only the die is involved in producing the striation marks.

If the die is transferred to a machine producing bags with the same physical attributes, i'm assuming the stiations and physical characteristics of subsequent bags produced would be similar.

In this case the use of the word "machine" would be erroneous.

Therefore, would the use of the term "source" in the conclusion be a more appropriate choice to include for this possibility?

I have included a journal link below on the manufacturing process of plastic bags for your reference.

Roux, C., Bull, S. & Olinder, S. PATTERN EVIDENCE | “Plastic” Bag Striations. Encyclopedia of Forensic Sciences 1181-1189 (2000)

Thank you very much for your time and assistance.

Best Regards,

« Last Edit: April 11, 2012, 09:24:48 PM by Joel »

Offline Andy Carriveau

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Re: Help on manufacturing marks conclusion: "machine" vs "source" ?
« Reply #1 on: April 12, 2012, 09:14:48 AM »

When examining evidence and I am unable to determine the exact origin of the tool mark, I report that "Tool marks observed on the ?????? are identified as having been produced by a common source".  I think that using "machine" says that that machine will always produce the marks that you are observing, when it is a part/tool within the machine or process that produces the marks.  So, my choice would be to use "source".


Offline Aaron Brudenell

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Re: Help on manufacturing marks conclusion: "machine" vs "source" ?
« Reply #2 on: April 12, 2012, 12:42:27 PM »
I like/agree with Andy's approach but you could also simply use the term "Tool" in a generic way as the harder of two objects or the source of said marks--that's the official AFTE definition but those outside of AFTE may not immediately presume that meaning.  Just be sure to define it that way at the point when it comes to interview or testimony.
Aaron Brudenell
Firearm Examiner
Arizona Dept. of Public Safety


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