More on supply chains and forensic science
Additional discussion; portions of this appeared in Houck, M.M., 2010. An investigation into the foundational principles of forensic science (Doctoral dissertation, Curtin University).
Clearly, there must be a difference in [pencil] sharpeners, else why would there be so many choices? Paco Underhill
We take the material world for granted. All the things that go into making a product and getting it to you (that is, supply chains) is enormously complex, probably beyond what we can readily comprehend. Even the simplest-seeming things are quite involved once you get into it. Entire books have been written about singular items, like salt, coffee, forks, and even (I kid you not) Twinkies. Study anything in the natural or material world and in short order, it can get away from you. This is why extending the forensic mindset to include supply chain information could greatly enhance the resolution of classification for evidentiary items.
Take aspirin, for example1
Standard aspirin tablets are made by adding corn starch and water to acetylsalicylic acid (active ingredient) along with a lubricant (such as hydrogenated vegetable oil, stearic acid, talc, or aluminum stearate) to keep the mixture from sticking to the machinery. The corn starch and water act as binding agents and filler; binding agents hold the tablet together while fillers (also called diluents) increase the bulk of the tablet to achieve a desired size. Various other diluents, such as mannitol, lactose, sorbitol, sucrose, and inositol, are added to chewable aspirin tablets, giving the tablet a pleasing taste and speed up dissolution. Either type of tablet may be colored; the United States has approved FD&C Yellow No. 5, FD&C Yellow No. 6, FD&C Red No.3, FD&C Red No. 40, FD&C Blue No. 1, FD&C Blue No. 2, FD&C Green No. 3, a limited number of D&C colorants, and iron oxides, among others.
The shape of an aspirin tablet varies with manufacturer to help identify their brand(s). The surfaces of the tablets can have a range of shapes and styles, such as flat, round, concave, or convex. The dosage of the tablet will, in part, determine the weight, size, thickness, and hardness. The upper and/or lower surfaces of the tablets may be scored with a shallow groove to facilitate breaking the tablet in half. Symbols, names, or letters may be stamped or engraved on the surface to identify the brand or the manufacturer.
Aspirin tablets are manufactured through a process called dry granulation (or slugging). The size of any one batch is dependent upon the scale of manufacture, the dosage, and the type of machinery used. The tablets are made in batches of the same dosage (amount of active ingredient) by the following processes. The ingredients are weighed separately in sterile canisters and mixed multiple times to blend the components as well as expel air.
The ingredients are then compressed into units generally from 7/8 to 1 inches (2.22 to 2.54 centimeters) in size called slugs. The slugs are pushed through a mesh screen to further mix the ingredients; smaller batches are worked by hand with a stainless steel spatula, while larger batches are filtered mechanically with a Fitzpatrick mill. Additional lubricant is added with a rotary granulator and sifter.
The aspirin tablets are created by compression in a machine called a punch and the process is often therefore called punching. Small batches are made in a single-punch and larger ones in a rotary tablet machine. On either machine, the process is similar, although the single punch machine is simpler in concept. On single-punch machines, the aspirin mixture is fed into a single tablet mold, called a dye cavity. The excess mixture is scraped away from the cavity. A punch—a short steel rod the same shape and size of the dye cavity—drops into the dye cavity and compresses the mixture between it and another, lower punch. The upper punch retracts and the lower punch rises and pushes the tablet out of the dye cavity. The machine resets and more mixture is fed into the dye cavity.
Rotary tablet machines work on the same principle except multiple punches work in a series and a number of dye cavities revolve as the mixture is dispensed. The upper and lower punches operate in sequence with the rotation of the dye cavities. Even a simple rotary tablet machine can easily produce upwards of 2 million tablets per year.
The finished tablets are moved in bulk to an automated bottling assembly line. The tablets are fed into polyethylene or polypropylene plastic bottles or glass bottles. The bottles, in turn, are packed with cotton, sealed with a sheer aluminum top, and then sealed with a plastic and rubber child-proof lid. A taper-resistant round plastic band is then affixed to the lid. The bottles are individually labeled, stamped with an expiration date, and packaged into shipping containers, typically cardboard boxes. The packages are then placed in larger cardboard boxes or palletized for shipping and distribution.
Even a simple, common product like an aspirin tablet has many dozens, if not hundreds, of steps that can add to the complexity of the material. A change, substitution, or variation in any one of the following may create a discernible difference between otherwise similar batches (not an exhaustive list):
This variety has direct and significant implications for forensic work should an aspirin tablet or tablets come under investigation for poisoning or tampering or in other types of combinatorial calculations from suitably-sized databases.
In short, everyday matters can be seemingly mundane but in actuality are incredibly complex. 2
Forensic science needs to learn the supply chains of its evidence
This extended discussion on a fairly simple commodity is offered as an example of the complex matrix of goods, processes, and variability inherent in each manufactured product. Forensic science needs to understand the ways things are made, naturally or culturally, before moving on to their forensic meaning.
The discussion on aspirin was developed from: Ecobichon, D.J., 1966. An Introduction to Pharmaceutical Formulation. The Canadian Veterinary Journal, 7(8), p.160.
Price, Sarah and Carr, Philip, Why the Archaeology of Everyday Matters?, pp1-13 in Price, S.E. and Carr, P.J., 2018. Investigating the Ordinary: Everyday Matters in Southeast Archaeology. University Press of Florida.