Guidance on Corrosive Agent Attacks

Guidance on Corrosive Agent Attacks

Introduction An incident involving an attack on an individual using an unknown liquid is often referred to as an ‘Acid Attack’; however any corrosive liquid can be used. Such attacks usually involve a corrosive chemical being thrown or squirted at an individual, which can temporarily disable a victim or in some cases cause severe burns and disfigurement. Extreme cases can result in fatalities. Most corrosive chemicals used in such attacks either have a very low or very high pH, where pH is a measure of the acidity, neutrality or alkalinity of a substance. It is usually measured on a logarithmic scale of 1 to 14, although, these are only arbitrary ‘bookends’ which are useful to illustrate such extremes. Water is regarded as being neutral and has a pH 7.

What are the most common acids used in attacks? An acid has a pH below 7 with pH 1 being considered very strongly acidic. Acids taste sour and can cause burns particularly if they are highly concentrated and have a low pH value. The most commonly encountered acid seen in Corrosive Agent Attacks tends to be sulphuric (sulfuric) acid in varying concentrations. This can cause severe burn injuries and damage to clothes even at relatively low concentrations. ‘One Shot’ drain cleaner is one of the products available that contains sulphuric at a very high concentration (approximately 91%). Whilst the sale of this acid has been stopped from most DIY stores it is still available on the internet. Battery acid is a solution of sulphuric acid at a strength of about 30% to 50% and can still result in injuries similar to those caused by the more concentrated ‘One Shot’ drain cleaner.

© Cellmark Forensic Services

CorosiveAgents/07/17

Page 1

What are the most common acids used in attacks? (cont’d) Other products available to the public include ‘Spirit of salts’ which is a concentrated (37%) form of hydrochloric acid and is available in DIY stores as a descaling chemical. Other lesser known acids, such as sulphamic (sulfamic), are being used more frequently in toilet cleaners as a descaling and a general purpose cleaning agent. Both of these acids have a pH of about 1 and can also cause some severe burns. There are many other acidic products and such as acetic ‘vinegar’ and ‘Kilrock’ (the latter containing formic acid which is present in the stings of wasps and ants). Although these are less corrosive than the acids mentioned previously, they can still cause irritation to the eyes and skin and also breathing problems. Nitric acid is infrequently encountered due to legislation regarding anything above 3% being a potential precursor for explosives. A note about hydrofluoric acid (HF). This is an extremely dangerous acid because, unlike sulpuric acid, it does not always appear to cause any burns outwardly BUT it is readily absorbed by the skin and will attack the body internally, dissolving bones and flesh insidiously if no treatment is given. It is used in glass etching kits. HF is one of the more difficult chemicals to identify and generally Cellmark Forensic Services does not accept these cases due to its hazardous nature. We advise police forces to consult their Health & Safety Departments regarding handling and antidote.

Alkalis/Bases A base (an alkali is a base that dissolves in water) has a pH greater than 7 with pH 14 being considered very strongly basic. Bases taste bitter and feel soapy or slippery and can cause damage to clothing and will cause burns like acids but their effects may not be felt as quickly. Alkaline chemicals such as ammonia solution and sodium hydroxide (‘caustic soda’) have been seen infrequently in chemical attacks. Caustic soda is usually sold as granules or pellets that can be readily dissolved with water. As such this can be present in a variety of different concentrations, most of which will a have a pH of 14. Whilst caustic soda may not cause the obvious ‘initial’ injuries seen by sulphuric acid it can cause extreme scaring to skin and damage the eyes more quickly than some acids. Sodium hydroxide is readily available in DIY stores either as caustic soda or can be present in degreasing agents and oven/BBQ cleaners. Ammonia solution is probably the most commonly encountered alkali and is widely available for stain removal in strengths of 5% to 10%. It is a very volatile chemical whereby the ammonia will readily evaporate from solution once exposed to the atmosphere. This has a maximum pH of about 12. However, this can still cause irritation to the eyes and skin and also breathing problems.



Page 2

Bleaches Bleaches that contain chlorine are based on hypochlorite. Some hypochlorite bleaches also contain sodium hydroxide and can have a pH of about 12.5. Bleaches that do not contain chlorine are based on hydrogen peroxide and other nonchlorinated compounds.

What type/style of container are these substances normally deployed from during an attack? Frequently corrosive liquids are transferred to a vessel with a siphon type nozzle such as a sports drink bottle or similar plastic receptacle. This can be carried innocuously and be used to direct the liquid at the intended target without the perpetrator coming into contact with the liquid themselves. There have been many instances of liquids, particularly ammonia solutions, being propelled from ‘Jif’ Lemon® containers or other similar squeezable bottles. The jet produced from a Jif Lemon type vessel can be readily directed onto the victim’s face and eyes causing temporary irritation and or blindness.

What are the best methods of recovery if a corrosive chemical is suspected as having been used? Ensure the approach H&S precautions are taken and gloves are changed regularly between suspects and victims to avoid cross contamination. • Clothing – seize as quickly as possible and place separated items into a nylon bag and swan neck to seal prior to placing into a polybag, as would be done for accelerant type cases. If the clothing is heavily contaminated, use two nylon bags prior to placing into a polybag. • Skin – samples will often be taken after medical intervention and therefore officers will need to work with the medics on this aspect. Swab any area, initially using dry swabs and then wet swabs. If these areas have been medically treated prior to sampling, advise your FSP, as this will likely affect any tests they undertake in the laboratory. In such instances examination of the clothing is likely to provide a more significant indication of the identity of the agent used. • Floor/walls – swabs should be used. Do not use fabric or paper or cotton based swabs as sulphuric acid will char and chemically burn these. If necessary, flocked swabs (polyester tip) can be used to sample stains. If there are pools of liquid use a plastic syringe to suck this up prior to decanting into a suitable glass vessel – see below for liquids. © Cellmark Forensic Services


Page 3

What are the best methods of recovery if a corrosive chemical is suspected as having been used? (Cont’d) • Liquids - these must be placed into a suitable container which depends upon is the corrosive substance suspected. Do not use metal containers. For most substances glass bottles with suitable glass stoppers or screw lids can be used. Thick polyethylene or polypropylene bottles can also be used. Place upright in a poly bucket, pack it out with vermiculite and replace lid securely. Some forces use their pathology kits for this. Then place into nylon, and then polythene bags. All items should be clearly labelled as containing/contaminated with a corrosive substance. • Please provide as much information about the potential attack and what affects the victim may have suffered, including timings and any account of what happened to their skin and clothing. This will help us in determining the type of chemical used in the incident. • Photographs, particularly of injuries and damage caused at the scene are beneficial.

How much substance do you require to make a positive identification? Cellmark Forensic Services requires only a few millilitres (ml) for identification. We are also able to determine strength/concentration, however, in order to do this additional analysis, we need about 50ml although we may be able to work with less in some cases. Residues of chemicals can be extracted from clothing and tested to identify the liquid used. Cellmark can perform a number of experiments to potentially determine the strength or concentration of the chemical used. Even if a liquid is not available we can conduct a series of tests using different concentrations of the suspected agent, on clothing, to provide an opinion on the maximum/minimum strength of such a substance used in an attack. We can extract acid/alkali/bleach and other chemical residues from swabs and therefore can provide an indication of the chemical used. However it is usually not possible to determine the strength of the substance used on these occasions. We advise using dry then wet flocked swabs on these occasions. A note about ammonia solution – this is a very volatile chemical that will be readily lost from clothing etc. Therefore it is important that swabs and clothing are taken as quickly as possible after any incident and packaged as outlined above using both secured nylon and polythene packaging.



Page 4

Additional Information Cellmark Forensic Services can provide guidance on the forensic aspects of these cases in relation to recovery, storage and transportation, however, we recommend that you consult your Health & Safety Department and HAZMAT team for Health and Safety recommendations. You might also wish to review the following link for controlled substances: https://www.gov. uk/government/publications/licensing-for-home-users-of-explosives-precursors/licensingfor-home-users-of-poisons-and-explosive-precursors#regulated-substances



Page 5