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June 10th, 2007
03:42 pmBecause someone asked recently...
Crime scenes are cordoned off as soon as the investigating team arrives. Generally CSIs carry the CRIME SCENE tape, so before they show up there's a uniformed officer or a couple of detectives hanging around to make sure nobody touches anything.
Victims and witnesses, if there are any, are immediately separated and watched individually. The cops will call the EMTs for anybody injured, if they haven't been called already. People with small injuries might be asked a few preliminary questions while getting stitched up and stuck with Band-Aids; people with large injuries are sent directly to the hospital. If the case is urgent enough or the injured person may be in further danger (i.e., domestic stabbing where the abusive spouse has not been found) a patrol officer or a detective will often go with them. EMTs don't care and half the time don't notice crime scene tape; they are busy dealing with people who might be bleeding out. Medical personnel of all kinds WILL stomp all over EVERYTHING. Any violent murder/attempted murder scene that has involved EMTs, paramedics or firefighters will involve bloody boot prints and equipment marks all over the place, which Sod's Law basically dictate will be on top of your most vital piece of evidence.
There are generally two CSIs at the scene of a major crime, at least. At least one will be holding a high-quality digital camera. Crime scene techs carry around a bazillion little numbered tags and small plastic rulers to use as markers for evidence. ALL crime scene photos are taken twice: Once with the tag or ruler in place for marking and scale, and once without, to eliminate the possibility that the CSI tagging might have obscured something. There will also be at least one CSI with a pad of graph paper, or if they have a large budget possibly a tablet PC, who is making a series of seriously OCD measurements of everything and sketching a diagram of the scene. After this is done, then the physical collection of samples and other tangible evidence begins.
Everyone wears gloves from the moment they get to the scene. After they've put on the gloves they touch nothing that is not evidence, and if any evidence gets on the gloves, they're changed. Techs with long hair have it pulled back as securely as possible. No matter how uncomfortable you are, you never open a window, tinker with the thermostat, or use the bathroom at a crime scene. If a tech is carrying a personal water bottle or something like that, it stays in the car outside or in the CSI's bag.
If there's a body at the scene, evidence collection is done first with the body present. If an autopsy will be done, which is standard procedure in most jurisdictions for any homicide, questionable suicide, or death from unknown causes, then the coroner's office sends someone to remove the corpse. Obvious evidence that might be lost if it's moved with the corpse might be collected by the techs at the scene; otherwise, hair and fiber evidence tends to be collected by the medical examiner as the body is prepared for autopsy. The medical examiner is also the one to ask about the nature, size and placement of wounds, or for a "tox screen", which is a standard panel of tests to detect medications or street drugs in the bloodstream.
Please note that a standard tox panel does not screen for ALL possible substances in the blood -- typically they screen for blood alcohol content and commonly abused drugs (amphetamines, cocaine, marijuana, opioids, barbituates, benzodiazepines). Other substances must be specifically requested. For example, in a suspected suicide case, if a prescription bottle marked for a month of Paxil (paroxetine) is found in the bathroom wastebasket, the medical examiner may request that the lab also check the levels of paroxetine and/or paroxetine metabolites in the blood. Screening can also be done for blood chemical levels, such as insulin or creatinine, if requested. Heavy metals are NOT routinely screened for, and if the medical examiner suspects poisoning by arsenic, lead, overdose of iron or other toxic metal those must be requested. (For this reason, many cases of arsenic poisoning -- accidental or intentional -- are overlooked. Acute heavy metal poisoning presents with symptoms of gastroenteritis at first, and does not add the characteristic hair loss and peripheral neuropathy until later. If the dose is high enough to kill within hours, then it may never be detected.) Please note that some substances are almost never screened for; LSD, for example, is completely flushed from the system well before hallucinations hit, and some paralytic agents like succinylcholine do not produce any unique metabolites and continue to deteriorate in the body after death.
At the crime scene, surfaces should be inspected, photographed, and dusted for fingerprints if necessary. Common places to find fingerprints include doorknobs (or, on swinging doors, the open side of the door between waist and shoulder height), stairway railings, drinking glasses, refrigerator handles and telephones. Porous or patterned surfaces do not typically hold prints well, although if blood or another strongly-colored, viscous substance is involved it is sometimes possible. Bloody prints are very fragile and may flake when moved, so they should be photographed as closely as possible, NOT lifted with tape. More ordinary fingerprints consist of oil that is naturally present on the fingers, and in a typical environment will last a few days before deteriorating. Prints are still developed with graphite or talcum powder (although it's also possible to get powder in other colors for contrast, and several varieties which glow under UV) and a sable brush and then lifted with squares of adhesive tape.
Prints on non-porous but textured surfaces, or on surfaces too fragile to properly dust (such as plastic grocery bags), are sometimes developed with cyanoacrylate fumes. (Cyanoacrylate is the generic name for a family of adhesives in craft stores under the names "Superglue" or "Krazy Glue", or for medical use under "Dermabond" or "Traumaseal".) The object to be printed is suspended or placed in a sealed environment -- labs typically use a terrarium under a fume hood -- and a small amount of cyanoacrylate is placed on a heat source. The cyanoacrylate vaporises at ~75C/180F and reacts with the fingerprint residue and the moisture in the air to produce a raised fingerprint that can then be dusted and lifted. Fumed prints do NOT come off, EVER, and can be lifted as many times as need be. (If the entire interior of a car needs to be printed, typically a small portable hotplate is used and the car simply closed up with the heated glue vapor for a few hours.) It is not recommended you breathe in superglue fumes, and the things being printed really do need to be in a container of some sort, as cyanoacrylate fumes tend to hug the floor.
Luminol is a chemical frequently used to uncover bloodstains that someone has taken a stab at cleaning up. Technically speaking, Luminol exhibits chemilumiscence in the presence of a suitable oxidiser, which in this case is the iron in haemoglobin. The idea is that when Luminol is misted onto a surface it reacts with any blood present, and glows a bright blue. No alternative light source is required to see this, and it can be captured with a darkened room and a long-exposure photographs. However, Luminol does not provide a positive test for blood -- because it will react with several agents (iron, copper, some bleaches), with non-human blood, and with the trace amounts of blood present in urine and faeces, the mere presence of a giant puddle-shaped glow is not enough to prove there was once a pool of blood there. (Although, just as an aside, because it reacts with copper, you CAN investigate the murder of Vulcans and/or Romulans with it. Just FYI.) Luminol itself does not destroy DNA, but because the blood it's usually used to uncover is invisible to the naked eye, typically there is not enough material left to perform DNA analysis on. (Cleaning solvents typically destroy DNA anyway, so if your perp has attempted to scrub the floor down the point is pretty much moot anyhow.) Luminol is somewhat caustic, and skin and eye protection are recommended when using it; it comes in small vials which are mixed with distilled water in a spray bottle (note: the DISTILLED part is important. If you tried mixing it with tap water, which often contains copper or iron from the environment or residential piping, you would pretty much get a bottle of useless but pretty blue glow). Interestingly, Luminol also reacts with cyanide, although it's not typically used for such at a crime scene.
Crime scenes can be cordoned off from a few hours to several days, depending on the investigation. The police do not take down the crime scene tape when the scene is released. The police also do not clean anything up; that responsibility falls to the owner, and if the owner asks the cops will typically have a list of local places which specialize in cleaning up crime and accident scenes. If for some reason an autopsy is not required on whatever corpses might be present, then the next of kin are responsible for getting a funeral home to pick the body up. Things that are taken as evidence disappear into the black hole of a police locker or warehouse and are never seen again, unless they are valuable enough to keep track of (cars, usually) or the next of kin make it a point to request that they be returned after the case is closed. The police also have no obligation to clean anything up after executing a search warrant, and typically don't.
There is nothing in a CSI kit that cannot be legally purchased and owned by private citizens in the US. Some of it is expensive, and might get you some odd looks, but none of it will get you arrested. To the best of my knowledge, there are no export restrictions on any of it. I have left out a lot of things in the basic review, so if anyone has questions, feel free.
Comments:
I would probably be going into forensics if not for two things: One, I am unbelievably lousy at biology/chemistry, so that's a no-go from the lab technician side. And two, I refuse to get near guns, so no law enforcement career for me either.
Forensic anthropology is an option, I suppose, but there was nowhere I could get to for an undergrad degree in it, so I'd be looking at grad school instead.
Forensic anthropology is an option, I suppose, but there was nowhere I could get to for an undergrad degree in it, so I'd be looking at grad school instead.
Still, even in terms of a hobby it's fascinating material. And, I can see what you mean about the gun side of things.
But, very, very interesting, still. Thanks for it.
But, very, very interesting, still. Thanks for it.
When I'm on-campus and get free (well, "free" with the thousands of dollars I pay them for housing) cable, I have a tendency to put on CourtTV and let that drown out the sounds of carousing idiots. It's basically 100% forensic how-tos, when they're not airing live coverage of a trial.
I watch CSI for Grissom, not for science. =) I try not to grind my teeth too much when watching Law & Order, though.
*laughs* I can imagine. Do you remember any particular egregious moments that made you want to pull your hair out?
CSI, not so much. That show very consciously uses technology that's "almost here" and I tend to think of it as a lil' bit sci-fi. I can't immediately think of anything that's ticked me off about an L&O episode, although I will say that Criminal Intent is *much* better about staying technically feasible than the other series are -- as well they should be, since Detective Goran's character is basically built on Sherlock Holmes and it would really rattle credibility if they involved sloppy forensics.
I can't really watch a lot of movies on the topic, though, for the same reason I can't really watch stuff like Hackers without totally cracking up. They're just so... silly.
I can't really watch a lot of movies on the topic, though, for the same reason I can't really watch stuff like Hackers without totally cracking up. They're just so... silly.
I was just thinking yesterday about the way some films use credible science, and how it tends to make the films age much better. I mean, take a film like WARGAMES (or, SNEAKERS) and compare it to the silliness of HACKERS. I mean, all of them are dramatized, but the extra detail in the first two films make a world of difference when watching them now.
Hmm...so now I know what to do if I suspect that there's a dead Vulcan or Romulan, but what if there's a dead Klingon? (Assuming, of course, that I would want to get involved in /that/.)
Anyhow - intriguing stuff. I love to watch Bones, except their investigations are way more complicated and specialized. But you'd think people would realize how hard it is to not get caught...
Anyhow - intriguing stuff. I love to watch Bones, except their investigations are way more complicated and specialized. But you'd think people would realize how hard it is to not get caught...
Haven't any idea what you'd use to investigate a dead Klingon. Nobody ever mentions just what it is, chemically, that makes their blood purple. =) It's noted several times that what makes Vulcan blood green is a coppery analogue to haemoglobin, and the Romulans are an offshoot of the Vulcans.
Incidentally, the English psychiatrist who periodically pops up in the most recent season of Bones is played by the Stephen Fry person I keep writing about. I actually have season one, but I keep forgetting to bring it to work and actually watch it...
Incidentally, the English psychiatrist who periodically pops up in the most recent season of Bones is played by the Stephen Fry person I keep writing about. I actually have season one, but I keep forgetting to bring it to work and actually watch it...
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