5.0 COLLECTING PHYSICAL EVIDENCE
Air pollution can usually be detected by the presence of coloured and/or noxious fumes, and sometimes, particulate matter. Air emissions require special investigation techniques and vigilance since they often vary according to the manufacturing period, time of year, time of day, direction of the wind, and so on. Here are a few tips for investigating air emissions:
• When an air problem occurs, note the time and the type of problem. Record experiences of breathing difficulties, odour, and material discomfort of any kind, such as that requiring closing a window on a hot night or eating indoors because of concerns about air deposition.
• Note wind direction (using a compass if possible) and estimate the wind speed (light, 0 to 5 knots; moderate, 5 to 15 knots; strong, more than 15 knots).
• Put a clean glass dish on a raised outdoor surface, such as a post or the top of a car, away from buildings. When the dish has collected particulate matter, place it in a clean envelope marked with the date (for analysis).
• Keep notes of your communications with a suspected polluter, government agencies contacted, and any other parties you engage with about the issue of concern.
• If possible, make a visual record of the pollution concern; for instance, take a photograph of a plume coming out of a stack.
• Contact the health unit in your area if air emissions appear to cause increased respiratory problems or ailments.
Liquid discharges come in many forms but are most commonly detected as leachate or effluent pipe discharge. Contaminated effluents usually lead to contaminated sediments as well.
Telltale signs that can help you begin or focus a water pollution investigation include colour, smell, iridescence, foam, algae blooms, changes in wildlife, dead fish, excessive sediment deposition, sewage fungus, and suspended solids.
Field work is often opportunistic; seeps that were present one day might not be the next; those that are toxic one day may not record as toxic another day. If you are waiting for certain environmental conditions to arise before sampling for evidence, you may have to wait for weeks or months. The key is to always be prepared to take samples and to treat them all as evidence for the case you are building. Sampling is warranted if a specific source is releasing discharge – such as chemical products, mud, petroleum, or sewage – that is entering a fish-bearing stream. If possible, sample where government agencies or the company has previously sampled, as well as at other sites. During one EBI investigation, an investigator discovered a toxic seep unknown to the manager of a site that had many such seeps.
Investigators can sometimes be fooled if they rely on observations to the exclusion of research and sampling. During another investigation, EBI investigators located two leachate seeps at a closed landfill. They collected samples from both seeps for toxicity testing on rainbow trout. A rusty orange liquid bubbled out of one seep while the other discharged a clear liquid that developed an oily sheen as it drained into the river. Investigators sampled both seeps because they were located over buried wastes. The fish subjected to acute lethality tests showed no ill effects when placed in the orange liquid but died within an hour in the clear liquid.
Further chemical analysis may reveal that all the samples are contaminated. A discharge that may not be acutely toxic to rainbow trout would still be illegal if it contained PCBs or other regulated substances, was chronically toxic to fish, or was lethal to other aquatic species (such as Daphnia).
Different circumstances warrant different types of sampling and hence, different equipment. Section 5.6 describes some types of testing and the corresponding containers needed. Although the procedures’ details may vary, the general approach, outlined in the example below, is the same in most cases.
Sampling example
On the first visit to a site, you witness a pollution occurrence: heavy sedimentation of a stream caused by uncontrolled erosion (i.e., it is raining heavily and the ditches are releasing dirty water into a stream). Back up your observations with notes, videotaped evidence, and photographs, along with samples of the waters affected.
Sampling equipment and procedure
• Bring at least six clean glass or plastic sampling containers 0.5 to1 litrein size, which you can obtain for free from any regional or municipal water quality testing facility or laboratory.
• Wear gloves and mark each bottle (at the time of sampling) with a permanent waterproof marker, including the following information:
• Date and time of sampling
• Your name or that of the sampler
• Sample identification code – indicate in your notes the exact location where you took the sample – give a GPS (Global Positioning System) reading, if possible.
• Rinse the container three times with the water from each location prior to taking the final sample. If sampling for a metal analysis, you may need to use containers that contain a preservative. Do not rinse these containers, and do not overfill them since this removes the preservative.
• When taking the sample, ensure that it is representative of the water you would like to test. Raise and lower the sample container through the water (or as far as you can reach) as it is filling.
• Seal each sample bottle with tape and initial the seal.
• Sample at the source, upstream where the water is clearer (above the point of sediment introduction), and downstream (below the point of sediment introduction).
In the case of a roadside ditch spewing heavily sedimented water into a stream, you would sample the ditch water before it entered the stream and the stream water both upstream and downstream from where the ditch discharged into the stream. These samples would show the discharge as close to the source as possible, the stream’s natural “background” conditions, and the impact site (the point at which the discharge enters the receiving environment). The discharge may well be your most important sample, but you must treat each and every sample as significant.
• If you suspect that the discharge may be toxic to fish and/or crustaceans (Daphnia), you should collect the required volume of effluent for bioassay testing (see section 5.6.2).
• Have your partner photograph and/or videotape you as you take the samples. This will show the court that you were indeed taking samples from the identified location.
• Draw a map of the site and note the sample identification numbers in the appropriate locations.
• See section 5.4 for details on note taking and Appendix C for an example of field notes.
• Handle samples appropriately, according to instructions provided by the laboratory (see section 5.6 for details).
• Finally, and just as importantly, you must know where the samples are at all times and be able to swear that no one tampered with them from the time you took them at the site to the time you handed them over to laboratory staff. This is known as the “chain of custody” (see section 5.5).
General tips
• For safety’s sake and to verify events, always conduct field investigations with a partner.
• Do not place yourself in a situation that could jeopardize your safety, for example, attempting to talk to someone carrying out a criminal offence.
• Protect your health from the hazards you are investigating. Wear appropriate protective clothing, gloves, and boots.
• Before going out sampling, you should have a good idea of the contaminants on the site, so you can bring the proper containers and take appropriate safety precautions.
• Read and/or consult experts about the impacts of these contaminants on the ecosystem.
• Know the physical layout of your target site and its history (maps and aerial photographs can be very helpful).
• Understand how your sampling work fits into your legal case (so you can use it to support charges under particular statutes and protect your evidence from attack once in court).
• Expect to sample and assay more than once (twice, at a minimum).
• Photograph and videotape the sampling work for the benefit of the press, as well as the court.
• Expect to come away empty-handed sometimes.
Field equipment
• This guide
• Appropriate clothing (e.g., rubber boots and rain gear)
• Gloves (latex or polyethylene)
• Notebook (waterproof, if possible)
• Pens, pencils, permanent waterproof markers (to identify the samples)
• Maps and/or charts (or draw one)
• Watch
• Sampling containers
• Sampling instruments (bucket, trowel, funnel, ABS pipe, and so on)
• Field testing equipment, if available (pH meter, thermometer, dissolved oxygen meter, and so on)
• Tape or custody seals
• Cooler and cool packs to store the samples
• Paper towels
• Garbage bags
• Camera and film
• Video camera, if available
• Global Positioning System (GPS), if available
• First-aid kit, including an eye-rinse kit
For more information on water quality sampling, see CCME’s Protocols Manual for Water Quality Sampling in Canada.
One of the difficulties a private citizen may encounter when investigating a pollution offence concerns obtaining physical evidence from private property.
Municipally, provincially, or federally owned sites are generally open to the public and do not pose the problems that privately operated sites do. However, during an EBI investigation at a provincially owned site, an employee told investigators that they were trespassing and that he would call the police if they did not leave immediately. The investigators pointed out that no fences or signs indicated that the land was private property, and that, in fact, they knew it was Crown land. The EBI investigators then left the site. Although polluters may resort to intimidation, distortion of the truth, and lies, don’t be tempted to use the same tactics. Their attitudes will not reflect well on them, whereas your calm, respectful, and fair behaviour will gain you support.
If you are sincerely unaware of site boundaries due to the absence of fences or signs, and if no one indicates that you are on private property, you may take samples at the site. However, if you know that you have entered private property and proceed nonetheless, you may be charged with trespassing, the information you gather may not be admitted into court as evidence, and you may lose credibility in the eyes of the court and the public.
Few options exist to counteract this problem, although you may be able to obtain samples without entering the site itself (for example, by taking samples of the effluent while standing in a river). From a sampling perspective, you may want to take your samples at the property boundary anyway since the court may not consider the site a natural environment (depending on the circumstances).
You may also request that the polluter take a “split sample.” In other words, the polluter gives you half of a sample that it has collected. Since the polluter’s refusal to do so may have a negative impact on its image, it may agree to provide you with a sample and even allow you to watch the sampling process. You can then bring that sample to a laboratory of your choice. Another option is to request regulatory agencies’ assistance in obtaining samples once you have accumulated other evidence that an offence may be taking place. Government investigators have powers that allow them to enter a site and obtain samples if they have reason to suspect an offence is being committed.
Note taking is an essential part of any investigation. Good notes describe in a few words where you were, when you were there, why you were there, and what you saw. They could also indicate who you spoke to and what was said. They should be clear and understandable because you may want to refer to them a year or more into the future (it can take this long, or longer, to get a case into court).
When investigating, take notes on waterproof paper such as Rite-in-Rain, which you can obtain from sports or forestry equipment supply stores. It would be disastrous if rain erased the hours you spent in the field recording valuable information. Take care to fasten the notebook to yourself with a string or cord, especially if you are working near or in a waterway. Although manufacturers of waterproof paper recommend writing in pencil because some inks will run if exposed to water, you may want to use a permanent waterproof pen to prevent the defence from attacking your credibility at trial.
It is best to keep your notes in a bound notebook with numbered pages to avoid the defence counsel suggesting that you might have altered them. Since you will have to disclose your notes to the defence counsel, you should not include personal details. As a witness, you may be allowed to refer to your notes while testifying to refresh your memory, but the court must be satisfied that you made them during or soon after the event concerned and that no alterations or modifications have been made since that time. Even if you are allowed to use your notes, you should also be able to demonstrate independent recall of the events. You will not be allowed to simply read out your notes to the court.
Alternatively, you can dictate your notes into a small hand-held Dictaphone.
Your field investigation notes should include:
• Your name and the names of anyone present in the field with you.
• Date, time of day, weather, and other environmental conditions (e.g., April 3, 2000; 10:35 a.m.; partly cloudy, air temperature2°C, water temperature6°C, snowpack light, heavy surface runoff from recent rain).
• Name, address, and/or location (in map units or geographic positioning units) of the site you are visiting and of any persons or corporations involved (e.g., Great Blue River, ABC Plant Inc.,9 Paradise Lost Road,Dark Water Town,Ontario).
• Any identifying marks (e.g., signs, logos, registration numbers) that indicate who is operating at the site and where those marks are located (e.g., on the side door of a pick-up truck, equipment, front gate). Such identifiers may be helpful in obtaining further information.
• Time and place of any photographs taken. Include roll number and frame (picture) number (e.g., Roll #2, Photo #16, Tributary #1,10:15 a.m.,10 mdownstream of culvert on Branch Road M2000).
• Features of the site, event, and type of activity involved which you can use to bolster your case (e.g., “This photograph shows the point in the stream where silt-laden ditch water is entering Tributary #1. Note that the water upstream from this point is running clear despite spring run-off conditions.”)
• A record of any steps potential offenders have taken to prevent the perceived problems. Noting preventative measures, if there are any, demonstrates you are conducting a fair investigation.
Review your field notes as soon as possible, while all the information is still fresh in your mind. You may have forgotten to write down an important observation you made at the site. Rewriting or typing out your notes when you get home may make the information easier to read, but be sure to keep your originals. Make copies of your final notes and store them in separate locations (e.g., at your office and at your lawyer’s).
See Appendix C for an example of field notes.
Any sample may become evidence; hence, you should handle all the samples in a manner that will allow you to identify them in court and to prove that no one has tampered with them. Here are the procedures you should follow:
• Your partner should witness the collection of the samples.
• You must properly label and sign the samples.
• For plastic containers use a permanent waterproof marker. You can also mark glass containers in this manner, but a glass scribe is preferable.
• Labels must be accurate. You should code the sample with a number, letter, and/or colour that corresponds to your notes. To avoid a potential conflict of interest at the laboratory and to ensure confidentiality, do not mark your samples with the name of the suspected polluter. Keep the codification simple and consistent because you may need to take repeated samples in an area, and you will need to be able to identify each one.
• You should be able to show the exact location from which you took the samples. You can record this information on a small-scale map (1:5,000 if possible; in cases involving forestry, maps are usually available at any forestry office) or on a reasonable hand-drawn facsimile. You should pinpoint the sampling location (a GPS is very useful for this) and mark it with the coded information that corresponds to the sample’s label. It may be a long time before you testify, so it is important to ensure that your notes are clear and accurate.
• You must keep the samples in a secure location where you can be assured that no one can tamper with them. A locked, cool, dark place is best. In most cases, samples are best kept cool (but should not freeze).
• If at all possible, bring the samples to the laboratory personally. If you must ship samples, use a licensed, bonded courier company and keep all bills of lading or waybills. Securely wrap the samples in a tamper-proof, impact-resistant package.
• If you transfer care of the samples to another person, be sure to obtain a written, signed statement to this effect. However, it is best to keep the samples in your own possession until you can ensure that they are in the hands of the laboratory personnel. Laboratories are familiar with this procedure and most have chain of custody forms for you to fill out when you arrive at their offices.
Chemical analysis will reveal an effluent’s composition and sometimes that may be sufficient. For example, the effluent may contain high levels of a known toxicant – in concentrations above what regulations allow – or a trace of a banned substance.
Laboratories can perform chemical analysis on liquid, solid, and gaseous samples, but not all laboratories perform every test available. Chemical analysis can be expensive, and you may have to test many samples, so it is important to select the tests wisely, based on the documentary information you have obtained. A reconnaissance scan is advisable on the first series of samples. By ordering a wide array of tests in the beginning, you will be able to make a more appropriate selection of tests for later samples you collect at the site. You may want to take more samples than you plan on having tested. The laboratory can sometimes hold these samples in case you need them for further analysis.
Although you may have obtained information that indicates high levels of particular contaminants at a site, do not limit the tests to those. Polluters will generally limit their analysis to what their release permits require, even though they may be aware or suspect the presence of other contaminants.
The results of the chemical analysis by themselves may not be particularly useful but they become revealing when you create a violation table and compare them with benchmarks such as concentrations indicated in the polluter’s Certificate of Approval (C of A) and governmental guidelines and objectives (see sections 4.3 and 6.2 and Appendices D and E).
Bioassay tests demonstrate an effluent’s overall toxicity. The individual pollutants in a discharge may be present in harmless concentrations, but in combination, they may have a cumulative or synergistic effect. Different laboratories will conduct different toxicity tests. Before you bring in your samples, call ahead to find out the tests a laboratory performs, the quantity of samples they require for the tests, and how you should obtain and keep the samples until they reach the laboratory. Some of the more common tests are briefly described below.
Before embarking on a sampling trip, confirm that the laboratory you are using is an accredited one by checking with the Canadian Association for Environmental Analytical Laboratories or by calling the laboratory itself. Also alert the laboratory staff that your sample may be used as evidence in a court case, so they will be prepared to testify. Obtain the proper containers from the laboratory and go over the sampling procedures. Most samples are best kept cool (4°C, not frozen) and away from light since some chemicals are photosensitive. Certain test procedures also require an analysis of the sample within prescribed time limits, and/or a complete filling of a sample container to prevent the loss of volatile components into the sampling container headspace.
When you compare the results of the chemical analysis with other data, you should ensure that the values are in the same units (see Appendix D, Table 4). Be aware that analytical instruments have precision limitations or detection limits. The detection limit for each test may be different and is normally indicated in the first column of the test results, next to the name of the substance being tested. The results for your samples should appear in the columns next to it.
Infrequently, the limit of detection will be higher than the release limits, rendering the test pointless if the concentration present is higher than the release limit but lower than the detection level. For example, if the guideline you are comparing your data with is 0.10 mg/L but the detection limit is 1.0 mg/L, the concentration of the substance may be 0.80 mg/L (eight times the guideline), but the analysis would only indicate that the substance was less than 1.0 mg/L. In the column under your sample name, this would be indicated by the symbol “is less than,” which looks like this “<” followed by a number or the letters LDL (less than detection limit) or LOD (limit of detection). This also applies to results you obtain from monitoring data or other sources. Just because the name of a substance appears on the analysis results does not necessarily mean it was present.
In some cases, the absence of a substance from monitoring data may be suspicious. For example, published company data might not contain any information about PCB levels, in which case you might ask yourself why not; if you suspect, given your investigation, that there may be PCBs, you should request that your laboratory check for PCBs in the sample.
Liquid samples
The following list of tests is not exhaustive but will provide you with some general guidelines. Always confirm with the laboratory what containers and quantities of samples it requires before sampling.
Conventional pollutants
|
Contaminant type |
Container type and size |
Preservative |
|
Ammonia and nitrogen compounds |
Plastic, 100 mL to 500 mL |
Keep cool |
|
Bacteria: fecal coliforms, E. coli, Streprococci, and so on |
Sterile plastic or glass bottle, 250 mL to 500 mL |
Sodium thiosulphate; leave air space; keep below 10oC |
|
Oxygen demand, biological (BOD) or chemical (COD) |
Glass or plastic, 100 mL to1 L |
Consult lab; fill to exclude air |
|
Phosphorus and phosphates |
Glass jar, 100 mL to 500 mL |
Keep cool |
|
Total suspended solids (TSS) |
Glass or plastic, 250 mL to1 L |
Keep cool |
Toxic pollutants
|
Contaminant type |
Container type and size |
Preservative |
|
Acids |
Glass bottle, 250 mL to1 L |
Keep cool |
|
Adsorbable Organic Halides (AOX) |
Amber glass with Teflon lid |
Consult lab; sodium sulphite and nitric acid, if needed; fill to exclude air |
|
Cyanide |
Plastic, 100 mL to 500 mL |
Consult lab; ascorbic acid, if needed; keep cool |
|
Heavy metals |
Plastic, 250 mL to 500 mL |
Nitric acid; keep cool |
|
Mercury |
Teflon or glass with Teflon lid, 100 mL to 500 mL |
Potassium dichromate and nitric acid; keep cool |
|
Organic contaminants (e.g., pesticides, polycyclic aromatic hydrocarbons, or PAHs,) |
Amber glass with Teflon lid,1 Lto4 L |
Consult lab |
|
Polychlorinated biphenyls (PCBs) and dioxins and furans (PCDD/Fs) |
Heat-treated glass,1 Lto2 L |
Keep cool
|
|
Radionuclides |
Amber glass with Teflon lid,1 L |
Consult lab; keep cool; if possible, place sample containers in lead-lined container |
Sediment and soil samples
You can place most sediment and soil samples in amber glass jars with Teflon lids. For most analyses, the laboratories only need about 100 g(about 10 tablespoons) of the material.
Bioassays are toxicity tests performed on laboratory animals using field samples. Generally, laboratory staff expose aquatic organisms (fish, invertebrates, algae) to a liquid effluent. Toxicity effects are various, but laboratories generally measure death, decreased reproduction, and decreased growth. Different laboratories perform different bioassays. Ensure that the laboratory you bring your samples to follows the protocols developed by Environment Canada and, if your case is in Ontario, the Ontario Ministry of the Environment for different species.
Lethal Concentration 50
Lethal Concentration 50 (LC50) indicates the concentration at which 50% of the animals placed in a given sample die (i.e., the lower the LC50, the more toxic the sample). To calculate the LC50, the laboratory places test animals in different concentrations of the effluent for a given duration (48 or 96 hours). Number crunching then produces a curve called a concentration-response curve. The typical concentration-response curve has a sigmoidal shape from which the LC50 can be calculated. Government protocols define the number of concentrations used, the number of animals, the conditions, and the duration of the test.
Pass/fail or single concentration test
A pass/fail or single concentration test is a simple bioassay in which some test organisms are placed in a 100% concentration of the sample and others in a control of clean water for a given duration (generally 48 or 96 hours). Government protocols define the number of organisms, the volume, and the test conditions.
If appropriate, a laboratory may conduct bioassays at a temperature other than that specified in the protocol (for example, at a temperature that better replicates field conditions).
Test organisms and required sample volumes
|
Test organism |
Volumes of sample required |
|
Rainbow trout or fathead minnows (less common and more expensive) |
For a single-concentration test: 20 Lto 50 L For LC50: 120 L You can collect samples in a lab-provided pail with a plastic liner and a lid. For large volumes, soft plastic containers with a spout and screw cap are available. |
|
Daphnia (tiny crustaceans) |
For a single-concentration test: 1 L For LC50:1 L to2 L |
|
Chironomid (midges) |
Used to test the toxicity of sediments, but because of its expense, not routinely performed. Consult labs for further details. |
Toxicity tests are also available for salt water environments (test organisms include urchins, oysters, and inland silversides).
Videos and photographs – visual documentation of environmental infractions — make good evidence. They also provide useful material to publicize your case and distribute to the media. For these reasons, visual evidence can be one of the keys to a successful case, but both videos and photographs present advantages and disadvantages.
Advantages
• Moving pictures show events or situations as they occur.
• Video cameras can imprint the date and time.
• Videos put the entire situation into perspective, including where you are (landmarks), where the problem is, and the scope of the problem.
• Video cameras allow narration of events as they occur.
• New cameras are light, compact, and can be concealed.
• You can view results instantly.
• You can distribute results to others (including the media) cheaply and easily.
Disadvantages
• Older cameras can be heavy and cumbersome.
• Improperly shot video footage can be jerky and difficult to follow.
• Lens options (wide-angle, telephoto) may be limited.
• Video cameras are expensive and fragile.
Things to remember when shooting video
• Always ensure that your batteries are fully charged and that you have sufficient memory before you begin.
• Check and recheck all camera settings (exposure, focus, colour, and so on).
• Always study your subject before you begin.
• Orient yourself to your subject and plan your shot (e.g., pan left, pan right, cut to, zoom in).
• Put the viewfinder to your eye, checking that what you see is what you plan to record, then, and only then, press the record button.
• Try to limit your shot sequences to between 30 and 45 seconds (an easily absorbed length of time within the average viewer’s attention span).
• When you finish your planned shot, stop recording before you take your camera away from your eye.
• Never use the camera to find something else to shoot while recording and looking through the viewfinder.
• When you are finished shooting a shot, ensure that the camera is no longer recording.
• Be cautious with sound. Ensure that those present are aware that they may be captured on audio or disable the audio feature completely when not narrating.
Things to remember when narrating a video
• Study what you are going to shoot, how you are going to shoot it, and what you need to say before taking the shot.
• Avoid scripts; be natural!
• Limit narration to topics such as your location and what the shot depicts.
• Avoid editorializing.
• Let the picture speak for itself.
Example of a good narration
“I am on Deleterious Creek, 300 metresupstream from where it joins Great Blue River. This shot (pan to) shows several trees that have been felled directly into the creek and abandoned. Here (pan or cut to) are the butt ends of the trees. Over there (pan to) are the matching stumps.”
Example of a bad narration
“I am on Deleterious Creek. This shot shows a bunch of trees that have been dumped into the creek and left. It is obvious that this has damaged fish habitat because I saw some fish on the downstream side of the trees, but none on the upstream side, so fish movement has definitely been blocked. It probably screwed up some good spawning area, too. Ooooh! I’m gonna get whoever did this, I’m so mad. They’re screwing up our fishery. Look at this mess. It looks like a war zone.”
Advantages
• Cameras are small and light.
• Some cameras have flexible lens capabilities (e.g., wide-angle, zoom, macro).
• Newer cameras are point-and-shoot, no thinking required.
• Photographs are easy to view and study (no slow motion or pauses required).
• Prints can be made for the media or posters.
• Photographs can be used for presentations.
• Photographs can be inserted into albums or reports.
Disadvantages
• Photographs give a limited, “snapshot” view of the world, making it difficult to put things in proper perspective.
• Some cameras have fixed photographic capabilities limiting their flexibility.
Things to remember when taking photographs
• Always ensure that you have fresh batteries in the camera, sufficient memory, and a flash unit.
• Check all settings (e.g., ASA, exposure, focus).
• Always carefully study your subject before you begin shooting.
• Orient yourself to your subject and plan your shot.
• Look through the viewfinder and make sure that you can see everything that you had planned to see.
• Centre your subject in the frame, focussing on the most critical element in the shot.
• When showing something where scale might be important, include something of known size in the frame for comparison (e.g., a ruler, a hand, a person).
• Use a flash when lighting is low.
• Use a tripod if you are unable to hold the camera steady.
• You can obtain wide-angled, panned effects by composing a mosaic: a series of shots that overlap side-to-side. It is important to know the capabilities of your camera and to be familiar with the coverage of the frame to cover the subject of a mosaic in as few pictures as possible. Make sure that the frames overlap. Often a good, wide-angle lens makes this technique unnecessary.
• Once you print your pictures, if your camera does not automatically put a date on them, write the date you took the picture on the back, along with your name and a description that matches your notes. In the course of an investigation, you may be at a site on several occasions; keeping track of when you took pictures is easy if you mark them appropriately. You may need several copies if the case goes to trial.
Environmental Bureau of Investigation 