In recent old ages at that place has been a important addition in the clandestine production and supply of illicit drugs within the UK. Last twelvemonth, a record 241,091 drug ictuss were made by the Police and UK boundary line bureaus, 6 % up on the old twelvemonth ( 1 ) . With this addition in drug trafficking the demand to set up connexions between drug traders and drug users has become of increasing importance ( 2 ) . As suspected illicit drugs are normally seized in the stuffs in which they are packaged ( 3 ) , one possible method that can be utilised to help in following their beginning is to transport out a thorough scrutiny of the packaging itself ( 4 ) .
Drug packaging analysis can supply highly strong evidentiary value when used suitably ( 5 ) . However, the evidentiary strength frequently varies depending on both the stuff in which the packaging is manufactured and the measure of packaging that is seized. In the past, literature articles have highlighted the assortment of stuffs that are frequently used to box and smuggle illicit drugs. This extended list has included: the liners of bags, Ananas comosus Sns, rubbers, paper, and foil ( 4 ) . However, doubtless the most common encountered packaging stuff in the forensic research lab is fictile.
The utility of plastic packaging analysis for forensic intents was chiefly documented in the eighteenth Century ( 9 ) . Research workers discovered that fictile stuffs were non wholly homogeneous ( 6 ) and as a consequence frequently contained drosss that could present alone characteristic characteristics. By developing methods in which these characteristic markers could be visualised, it became possible to compare fictile stuffs seized from different beginnings. This cardinal principal revolutionised the field of boxing analysis as strong evidentiary connexions between points of plastic could now be established and used in Court ( 5 ) .
In order to to the full understand and appreciate how these characteristic fabrication Markss originate, and besides how they are exploited forensically, it is necessary to grok both the rules that underlie fictile chemical science, and the procedures involved in fictile industry.
Aim of this reappraisal
Plastics Chemistry
Plastic is a byproduct of the crude oil industry that was originally developed as a cheaper option to natural stuffs such as wood and metal. The chief ingredients that are required for fictile industry are organic monomers and plasticizers. A monomer is a low molecular weight molecule that has the ability to chemically adhere to other monomers via strong covalent bonds, organizing a concatenation of monomer units, known as a polymer ( 5 ) .
In the industry of fictile packaging there are four chief polymers that are in usage today, these are: polythene, polypropene, polyvinyl chloride, and polythene terephthalate ( 4 ) .
Polyethylene terephthalate ( PET ) is a high strength short-chain polymer that is most often used in the production of soft drink bottles. This is chiefly due its ability to defy bleaches, detergents, and heat every bit good acids and bases ( 5 ) .
Polyvinyl chloride ( PVC ) , a polymer formed from many vinyl chloride monomers and of course exists as a stiff construction. As a consequence it is frequently necessary for the add-on of assorted plasticizers, like dioctyl adipate ( DOA ) , to do the polymer more flexible. Due to the demand of plasticizer add-on this type of polymer is now seen less often in nutrient packaging stuffs as research has shown that these plasticizers may leach into the nutrient merchandises ( 5 ) .
Polypropylene ( PP ) is a simple polymer that is formed from the polymerization of propene monomers. It is chiefly used in the industry of clear movies and micro-cook packaging ( 5 ) .
Polyethylene ( PE ) , normally known as polyethylene, is an ethane polymer from which most plastic bags and movies are manufactured. As the bulk of fictile drug packaging analysis is performed on plastic bags and movies, polythene is of major involvement in forensic scientific discipline. The polymer is really various and can be categorised under assorted classs depending on its denseness ( 5 ) . Low denseness polythene ( LDPE ) , of denseness scope 0.916 to 0.925 gms per cubic centimeter, exists with a more flexible construction and is chiefly used in the industry of cleaving movies and bin bags ( 5 ) . On the other manus, High denseness polythene ( HDPE ) , of denseness scope 0.941 to 0.965 gms per cubic centimeter, is composed of smaller bifurcate monomer ironss and therefore exhibits a more stiff construction. HDPE is normally used in the industry of milk bottles, deep-freeze bags and shopping bags ( 5 ) .
With such a big diverse scope of polymers and additives that are now available to the plastics industry the opportunities of two separate mills fabricating indistinguishable merchandises is reduced. Knowledge of this is an highly utile tool for the forensic scientist as it opens up the possibilities for set uping connexions between plastic samples based on their chemical composing ( 14 ) . Detailss of current chemical comparing methods will be covered in full subsequently in this reappraisal.
Plastic bag and movie industry
At the beginning of the fabrication procedure virgin or reprocessed rosin pellets are positioned in a cylindrical extruder where they are assorted with pigments and other additives. The mixture is so heated to about 250oC to bring forth a homogeneous, syrupy fluid ( 5 ) . Before the syrupy fluid undergoes any farther processing it is filtered in order to take any big drosss that may be present. Once this is achieved there are two possible bulge processes that the polymer can undergo, these are known as Cast or Blown bulge ( 5 ) .
Cast bulge
In this simple procedure the syrupy polymer fluid is fed through a consecutive dice. As the dice is in the signifier of a horizontal slit, a level sheet of polymer movie emerges that is of equal thickness to the dice slit ( 5 ) . The level polymer sheet is so cooled and hauled off through a series of rollers before being wound up on to a axial rotation ( Figure 1 ) .
Figure 1: Conventional diagram of a standard Cast bulge procedure.
Blown bulge
The Blown bulge procedure is more common than Cast bulge and is by and large the method of pick for the production of plastic bags ( 5 ) . In this procedure the syrupy polymer will come in a annular dice where it is forced around a spindle ( a rod found inside the dice ) , shaped into a arm and extruded through the dice gap in the signifier of a fictile tubing. The tubing, while still in the molten province, is so farther expanded to a “ bubble ” or excavate cylinder by blowing pressurised air through the Centre of the spindle to the interior of the “ bubble ” , therefore leting the plastic to be stretched to the desired breadth. As the hollow plastic tubing is forced upwards it cools down and is eventually collapsed by a series of “ nip rollers ” before being wound on to a axial rotation ( Figure 2 ) .
Figure 2: Conventional diagram of a standard Blown bulge procedure.
Upon completion of both Cast and Blown bulge there are a figure of possible results for the fictile sheet. Quite frequently it is merely the instance that the plastic is wound up on to a axial rotation and stored. However, sometimes it can be transported to a different location to undergo farther industry. Extra industry processs may include printing, folding, gusseting, add-on of grips, heat waterproofing and film editing. Depending on the type of bag desired by the client will find which of these procedures occurs.
Distinguishing characteristics of plastic bags
As a direct consequence of the fabricating procedure many distinguishing characteristics are for good incorporated in the fictile stuff. It is these fabricating Markss that are so compared in order to set up whether or non two fictile packaging ictuss have arisen from a similar batch or trade name of manufactured plastic. Examples of such Markss include, striations, pigment sets and emphasis sets.
Strias
Strias on the fictile arise as a consequence of squeeze outing the plastic movie through the dice, spindle and to a certain extend over the rollers. This type of physical feature is frequently observed on both the outer and interior surfaces of the plastic movie. Stria Markss may be farther divided into die lines and dyer’s rocket lines ( 5 ) . Weld lines ( knit lines ) arise when drosss get trapped in the dice and are less normally encountered in forensic scientific discipline. Die lines nevertheless, are comprised of a uninterrupted series of longitudinal indentures or bulges and have been shown to be present throughout the plastic fabrication tally ( 8 ) . Die lines are thought to originate as a direct consequence of the bulge procedure. If the handbill dice, through which the plastic is extruded, exhibits imperfectnesss in, or besides, a physique up of plastic on its surface, these Markss will be incorporated onto the liquefied plastic as it flows over the die surface ( 8 ) . As a consequence of this, it is thought that plastic bags which present similar dice lines must hence hold originated from the same blown bulge setup on the same fabrication tally ( 8 ) .
Stress sets
During blown bulge, pressurised air is blown through the spindle to organize a hollow plastic tubing. As this occurs the liquefied plastic is stretched. This stretching of the plastic is thought to give rise to alone horizontal runs that run across the plastic movie. These runs are known as emphasis sets and they are highly utile fabrication features. By comparing the emphasis bands present on different plastic stuffs it is possible to find whether or non they have originated form the same fabrication tally, and besides to some extent, the propinquity at which the bags have been manufactured to each other.
Pigment sets
Sometimes dyes or pigments may be added along with the fictile pellets at the beginning of the fabrication procedure. When uncomplete homogenization of these substances occurs, pigment sets may originate in the plastic. Pigment sets are normally orientated in the same way as movie production, and they are really utile in linking big Numberss of fictile points with a common beginning ( 5 ) .
Besides the above mentioned normally ascertained physical characteristics in plastics, many other alone placing features may originate by other agencies. Sometimes the plastics used in the fabrication procedure can incorporate random drosss such as C, rosin, or grit ( 5 ) . When these drosss are non isolated during the filtrating procedure they become incorporated in the movie and can show as either dark or light musca volitanss of plastic ( 5 ) . In industrial footings these are referred to as “ fisheyes ” . “ Fisheyes ” frequently appear together with “ arrowheads ” , which are perpendicular runs in the plastic that radiate out from the “ fisheye ” ( 5 ) . Together these alone characteristics can be used to categorize plastic bags that have been manufactured together on the same fabrication tally. However, these types of industry Markss are of limited value as they are non frequently seen by the forensic scientist. If these Markss are present in the plastic it is by and large non of sufficient quality to be released to the client and is usually scrapped.
Construction features
Aside from emphasis sets, pigment sets and striations, some alone identifying Markss may be introduced to the plastic as it undergoes farther industry. Together these Markss are known as building features and they must non be overlooked. Such characteristics can be used in concurrence with physical features to find the beginnings or relationships of differing plastic bags that are under probe. Many common building characteristics that are frequently examined by the forensic scientist include: the coloring material of the bag, any printing on the bag, the type of seal on the bag, whether heat sealants have been used to cut or heat seal the bags, and besides any perforations that may be present on the bag.
The forensic scrutiny of plastic bags and movies
Like any other forensic scrutiny the rating and comparing of plastic bags and movies will follow a stepwise protocol. By and large this involves the logical patterned advance from a simple, non-destructive analysis through to the usage of more elaborate and frequently more destructive techniques. It is non really possible to depict the exact methodological analysis used in the scrutiny, as in pattern this differs harmonizing to the resources available, the content to be examined and besides the personal penchants within each of the forensic suppliers ( 5 ) . However, it is possible to give a brief description of the current methodological analysiss that have been developed for the psyche intent of distinguishing between assorted fictile stuffs.
Physical/mechanical tantrum
One of the simplest methods, yet one of the strongest in footings of evidentiary value is that of showing a mechanical tantrum between the cut edges, or between the emphasis and decease sets of two fictile bag samples. Direct mechanical tantrums can once and for all set up whether or non two plastic bags where manufactured consecutive on the same fabrication tally.
Interference grid
Using this straightforward, non-destructive setup, it is possible to visualize some of the surface fabrication features described above. An intervention grid merely consists of lighted, jumping black and white lines. When the grid is placed behind the sample in inquiry, any imperfectnesss in the plastic will blockade the visual image of the grid and as a effect will do the distinguishing characteristics of the plastic seeable. Following this, the characteristics can be easy photographed and a comparing made ( 12 ) .
Incident, transmitted and oblique lighting
By changing the placement of a light beginning it is possible to utilize incident, transmitted and oblique lighting to light fabrication Markss on plastic. Transmitted light is peculiarly utile for visualizing characteristic characteristics on pigmented plastic, such as pigment sets and “ fisheyes ” . Incident lighting is best for visualizing abrasions and publishing on the surface of plastic, and eventually oblique lighting is ideal for visualizing fabrication Markss on crystalline plastic.
Additionally, incident and transmitted light microscopy can be used to analyze any printing that is present on the plastic and besides the texture of the plastic itself ( 5 ) . This signifier of microscopy is utilizing carried out on a stereomicroscope.
Polarization tabular array
As plastic is extruded and so strained over a series of rollers the polymers within each bed become orientated in line with the way of bulge. This makes the beds of fictile birefringent ( 13 ) . As a effect, differing coloured forms present on the plastic may be viewed. This can be achieved by utilizing crossed polarised filters, in which two linear polarizing filters are placed at right angles to each other. If the plastic packaging stuff is placed between the two filters at an angle of 45o, coloured forms will be observed on the plastic that expose the fabricating history of the packaging ( 4 ) . This method can besides be utilised to visualize other fabricating Markss including abrasions or roller Markss ( 5 ) . When utilizing this method it is besides possible to snap the colored forms for scrutiny at a ulterior day of the month.
Photography
There are many types of picture taking that may be used to visualize characteristic characteristics on plastic bags and movies. These scope from simple methods such as taking a picture taking of the packaging to more complication methods like Shadowgraph and Schlieren picture taking.
Shadowgraphy is simple optical technique that may be utilised to visualize and compare bulge Markss, heat-sealed borders, and cut borders on different samples of crystalline polyethylene bags and sheets ( 5 ) . In Shadowgraphy all that is required are a individual point light beginning and a screen onto which the shadow may be projected. The radiogram is produced by go throughing the light beams through the crystalline plastic. Any impurities nowadays in the plastic will do a localized alteration in refractile index and therefore will disperse any light beams hitting this point. As the visible radiation is no longer permitted to go through through this subdivision of the plastic a shadow will be cast on the sing screen ( 11 ) . The attendant radiogram may so be recorded by either manual picture taking, electronically, or developed on photographic movie or paper ( 5 ) .
As Shadowgraphy is a non destructive method, the sample will non be damaged during the process and other visual image methods may be used to complement this technique ( 4 ) .
As an option to Shadowgraphy, Schlieren picture taking may be used. Although the rules or this technique are similar to Shadowgraphy the chief difference between the two procedures is that Schlieren picture taking makes usage of lenses, mirrors and a knife border filter to bring forth an image ( 11 ) . Similar to before, a point visible radiation beginning is used, nevertheless this clip the visible radiation is passed through two sets of lenses. The fictile sample under probe is placed between these lenses, in an country known as the Schlieren field ( 5 ) . Additionally, at the focal point of the 2nd lens, a knife border filter is incorporated that directs scattered light beams towards the imagination screen and diverts uninterrupted light, therefore making a shadow. The captured images may so be recorded in a similar manner to that in Shadowgraphy ( 5 ) .
Magna Jet Black fingerprint pulverization
It is possible to utilize fingerprint pulverization to visualize characteristic characteristics on plastic. However, this method has been shown to interrupt any farther chemical analyses being carried out on the plastic. Consequently, it is advised to be used merely as a last resort when other non-destructive methods have been trialled foremost ( 10 ) .
Chemical methods
In add-on to the above discussed physical methodological analysiss there exists a diverse scope of chemical techniques that can be utilised to characterize the makeup of plastic packaging. Chemical analysis is an highly effectual tool as it allows the designation of the base polymer, additives, every bit good as any pigments or dyes to be identified ( 5 ) .
Wide angle X-ray diffraction ( WAXD )
Fourier Transfrom Infrared Spectroscopy ( FTIR )
Fourier transform infrared ( FTIR ) spectrometry is a measuring technique that allows one to enter infrared spectra. Infrared visible radiation is guided through an interferometer and so through the sample ( or frailty versa ) . A traveling mirror inside the setup alters the distribution of infrared visible radiation that passes through the interferometer. The signal straight recorded, called an “ interferogram ” , represents light end product as a map of mirror place. A data-processing technique called Fourier transform turns this natural information into the desired consequence ( the sample ‘s spectrum ) : Light end product as a map of infrared wavelength ( or equivalently, wavenumber ) . As described above, the sample ‘s spectrum is ever compared to a mention.
Infrared spectrometry
Thermal desorption capillary gas chromatography
x-ray fluorescence spectrometry
thin bed chromatography
microspectrophotometry
neutron activation analysis
isotope ratio mass spec ( IRMS )
UV-vis
Differential scanning calorimetry
Pyrolysis-gas chromatography
Gas chromatography – mass spec
Elemental analysis
It is uncommon for a individual trial to unambiguously place a sample of fictile packaging with its fabrication batch, works, or geographical location, or to tie in one sample with ( or separate it from ) another. To construct a conclusive position of the birthplace of a sample of fictile drug packaging that will stand up as grounds in a tribunal of jurisprudence, it will by and large be necessary to compare a scope of physical and chemical belongingss of the sample with those of similar plastics of known beginning
Sections still to finish:
The value of fictile bag grounds
Conclusions/ my work
