CSI demystified!

看板CSI作者Topanga (Believe, dream, try)時間19年前 (2006/03/28 11:13)推噓5(5推 0噓 1→)

留言6則, 4人參與討論串1/10 (看更多)

之前收集大家的問題，去問現實生活中的CSI，已經得到回覆了而且...非常的落落長....... 我先把回答貼過來，請善心人士有空幫忙翻一下囉。（會不會直接按end啊 XD）看來這位大哥叫做Larry, 在德州的 crime lab 工作專精的是有關毒品方面的檢驗所以有些問題他也只能就他所知回答，畢竟術業有專攻，他在回答中也有提到，現實生活中的 CSI 其實是比電視上分工還要細，而不是像電視上那樣每個人都是全才。（其實我覺得本店第一季還有根據個人的專長稍做著墨，後來變得好像每個人都什麼都會）當CSI有什麼條件，我覺得可以看一下，看完以後會覺得這真是個崇高的工作 ^^ 不過據這位大哥說沒有身高限制，也沒有視力限制，他是作毒品分析的，所以有化學方面的背景是最好的，不過看你是要作哪方面的分析，所需要的背景也各有不同。他說真正跑DNA分析其實不會太久，真的久的是準備分析的樣本，而大多數實驗室之所以會花很多時間，是因為案子積太多了！ >What does it take to be a CSI? Is there a requirement on height? A: To answer the 2nd question first, there's no height requirement for forensic scientists in real life. (Nor, luckily for me, is there a photogenicity requirement. LOL) Back to the first question, I really think the most important requirement to be a good CSI is to have an inquiring mind, and by that I mean be interested in a lot of different subjects. You also have to be meticulous (since recording the results of the analyses, whether it's weights of drugs, or allele matches in DNA, or whatever, has to be done as accurately as possible), patient (because despite the glamorous image portrayed by the TV show, a lot of the work is very repetitive), detail-oriented (able to assess and keep in mind a wide range of tiny facts) yet also able to see the "big picture" (don't lose sight of the overall goal, just because you're concentrating on small details at any particular moment), have good laboratory technique (since sloppiness can lead to incorrect results or incorrect assessments of the results), be objective and truthful (since you will testify as a forensic expert in courts of law about the results you obtain - and you must favor neither the prosecutor nor the defendant, but allow your scientific observations to speak for themselves), able to explain complex analyses in lay terms (because by and large, the juries who will hear your testimony are *not* scientists), not be overly shy (you will be explaining your work and results before a jury of about a dozen people, as well as the judge, court reporter, and prosecuting and defending attorneys, and perhaps court visitors as well - and since we have an "adversarial" legal system in the U.S., the defense attorneys can try to discredit your work or your results - and may even resort to somewhat personal attacks), and fairly quick-thinking (to respond to the attorneys' questions; the defense's questions in particular are unlikely to be "scripted"). It sometimes helps, too, to be a little thick-skinned. Not only are crime scenes sometimes (often?) messy to filthy to nasty, but also you'll have some limited contact with the less-than-stellar members of our society - or at least you may be working with their body fluids. So in addition to all the technical stuff, you also have to keep in the back of your mind an awareness that the material you're working with may be infectious, or toxic, or explosive. You have to be careful, and it boils down to remaining intellectually alert even if the task at hand appears at first glance to be the same test you've already run 10,000 times in your career. If your goal is to analyze "controlled substances" (drugs), it would be a good idea not to take them for a test drive in your personal life. The U.S. DEA (Drug Enforcement Administration) *says* that "limited, youthful experimentation with marijuana" will not necessarily bar you from being hired by them - but believe me, the competition for the positions is so intense that it will in fact be the kiss of death - and experimentation with any other drug also will definitely knock you out of the race. Every forensic organization I know of automatically excludes applicants that have any felony conviction - so, also avoid DWI (driving while intoxicated), as well as any more serious illegal activities (drug sales/manufacture, murder, rape, forgery, burglary, bank robbery, etc - they're all no-no's). In other words, live your life so as to be able to withstand a complete and detailed background investigation. >What kind of background do you have to have (e.g. biology, chemistry, physics, etc.) A: For drug analysis [which is my specialty] a strong chemistry background (B.S.) is the best. There are universities that offer a "forensic science" degree, but in my opinion these programs are not sufficiently rigorous in hard science and math. If you want to become a DNA analyst, then you should have a background in biology, including courses in genetics and molecular biology; a course in statistics also might be good to have, since your testimony will include explaining the probability of DNA matches to a jury of laypeople. (And just like in graduate seminars, you should know roughly 5-10 times as much as you say in your "prepared" speech.) For forensic computer analysts (for example, money laundering schemes, conspiracies, drug dealers, porn rings including child porn, hackers/crackers, etc) obviously you should have an in-depth background in computers, including knowledge of a number of different operating systems, applications, some programming languages, and all sorts of peripherals; detailed knowledge of storage components' operation (hard drives, CDs, DVDs, floppies, ZIP drives, etc), and at least a working knowledge of networking software and equipment. There is forensic software that will help you, and it's been vastly improved since the early days, but you'll still need to be very detail-oriented and meticulous. For trace analysis (hair, fibers, paint, cloth, paper) chemistry is still a good background, since the laboratory courses teach you to be meticulous and expose you to the scientific method - which really is just a framework to guide you in your analyses. For the firearms/toolmarks subdiscipline, an interest in guns is useful, but you also have to be able to visualize how things compare (do striations on a particular "evidence" bullet match the ones on another bullet fired from the suspect weapon?) or how they fit together (to see, for example, if the marks on a window frame could have been made by the crowbar submitted as evidence in the case). Some other disciplines such as fingerprint analysis and questioned document analysis don't so much require a hard science background as the ability to discern small details and small differences. Fingerprint analysis has been automated through computer matching, but the final comparison is still done by human analysts. Other subdisciplines such as explosives investigations are pretty much "OJT" (on-the-job training) fields, but again a good background in science will give you the sort of disciplined analytical approach that will prove useful. >How long does it take to get a DNA result? A: The actual analysis doesn't take terribly long - say overnight. Preparing the samples for analysis takes longer - a day to a week or more, depending how much evidence is submitted. (The huge number of samples from the 9/11 incident and the Oklahoma City bombing took many months to process.) The reason it takes most labs a long time to return results is that nearly all of them have tremendous backlogs of evidence waiting to be analyzed, and unfortunately the trend is that the backlogs are increasing rather than decreasing. In our lab, it may take only 30 minutes to actually analyze a particular exhibit - but it takes about 6 months to work through all the other cases that were submitted before that one. Our turnaround time has increased from about 2 months to about 6 months over the past 2 years, mostly because we've had a huge increase in the number of cases that are submitted to us for analysis during that time. >Is it still possible to test for DNA on a cotton swab if it had been sprayed with luminal? A: This isn't really my field, so I'm not sure. It depends on whether the solvent for the luminol "denatures" or decomposes the DNA. I seem to recall that when luminol is used on a surface (a painted wall, say) that had blood smear on it, DNA can still be recovered from the area where the luminol indicates blood was present. But I may be thinking of visually-apparent (*without* luminol) blood spatters. DNA would quite likely be recoverable from those, if they're not too old. >Is it really possible to enhance the images on surveillance tapes the way they do on the show? A: This is possible, yes. Good photo "retouching" software does the same sort of thing (increase/decrease contrast, increase sharpness) and more specialized software can even convert small differences in color in the original image to contrasting colors to provide the effect of even more enhancement. >How much can you enhance the images? A: Again, it's not my field, but I suspect it's less than what they show on CSI. I could be wrong, though - recall that many of the photo enhancement techniques (software) were originally developed for military applications and clandestine intelligence ("spy") operations, and those are quite sophisticated. How much of that technology has filtered down to the law enforcement/forensics community, I'm not sure. It's probably a safe bet that the military/intelligence software is better than what's available to forensic analysts, which is better than what's (usually) available to joe-on-the-street. >What do you think about the show (the CSI franchise)? A: If you keep it in perspective, that at its heart it's *entertainment* - then in that sense I enjoy it. In terms of the science, it seems fairly true-to-life most of the time. In terms of the amount of time it takes to analyze a case, it takes a lot longer and is a lot less glamorous than the way it's portrayed by the show. Most forensic analysts nowadays are more specialized than is shown, but as I said earlier, wide-ranging interest in and knowledge of a variety of subjects can be a very useful talent. The Journal of Forensic Science is probably available to you at the university library, and will show you the wide variety of subjects that the field covers. Nowadays nearly all forensics people are specialists in one or at most only a few sub-disciplines of the field. >Do more people get into this career because of the show? A: I think interest in the career field has definitely been heightened by the show. The downside is that the work's not nearly as glamorous as the show makes it seem. Sure, especially early on in your career, there's a bit of the "snob factor" that you were selected to work in a career that has its interesting moments. I hadn't had any exposure to street drugs before I began working for the crime lab, so that was interesting for a few months - but like any job, there is so much repetition of seeing "the same old thing" that you have to work to maintain your interest. There are various ways to do that; one is to remain focused on the job at hand and consider each case as a fresh challenge to be solved (and keep in mind that *somebody* - at least the defendant if not his/her family) is vitally interested in your results and in being assured that you did your best to be objective and truthful); another is to expand your knowledge to other forensic sub-disciplines, by talking with your colleagues, attending seminars and conferences, getting additional training, and reading. Think of the rock stars from the 80's or even the 60's - how do they keep their renditions of the standards their group has sung 1000s and 1000s of times, fresh for tonight's concert? It's a combination of training, self-discipline, and living in the moment. It's the thrill of meeting the challenge and solving the problem. I think that's the same for any job that you plan to stick with long-term - you sort of have to devise ways to keep yourself interested and challenged and fresh. >Is it more difficult to solve the cases because of the show? A: I don't think it's more difficult to solve most of the cases. I do think the public has an expectation that *any* case can be solved by the crime lab, and that's not true. Nor are we infallible. Despite our very best efforts and very best intentions, despite all of the quality checks we build in to the system, in a very small number of cases, we make errors. (That fact is always in the back of my mind, and it just makes me all the more determined to do my very best to be accurate and truthful in my interpretations of my analytical results.) There's also a mistaken impression that all or nearly all cases can be solved _quickly_ by the lab, and that's not necessarily true. >What is the percentage of cases solved using forensic techniques? A: I don't have a number, but usually forensics is an *adjunct* to plain old detective work. For example, in my case, I don't go out and bust drug dealers; all I do is analyze their wares. If the case goes to court, all of the observations and actions by the patrol officers and the narcotics detectives (what they did and why they did it) has to be related to the jury, and comes under scrutiny by the defense lawyers. There has to be "probable cause" for the arrest. Custody of the evidence has to be controlled and documented, to insure that it wasn't contaminated or tampered with prior to its arrival in the lab. My analysis of the evidence is just the end of the whole process - and if the analysis shows that there were no drugs present after all (the guy was selling sugar instead of meth, maybe), then the whole case collapses and the charges are dismissed. If drugs were actually present, the defendant may decide to plead guilty and not go to trial. Even if there is a trial, if the defense counsel is able to show there was a break in the chain of custody of the evidence (such that the evidence I analyzed might *possibly* not be the same evidence that was seized from the defendant at his arrest) or that there was not legal probable cause to justify the arrest, then the case ends. If all the other requirements are met, then the prosecutor still has to show that I'm qualified as a drug analysis expert (this is done based on my educational background and experience) before I can testify about how I analyzed the evidence and what the results of my analyses were. My analysis is like the final piece in the puzzle. In cases of rape or murder, forensic analysis can become the linchpin to the entire case. There have been a few cases where a person was convicted based on old (pre-DNA) serological techniques, and subsequent re-analysis using modern DNA techniques actually *exonerates* the person. There are also some cases that have been solved via CODIS (Combined DNA Indexing System - a national DNA database) matches, where traditional investigative/detective techniques have run into a dead end. Usually though, forensics provides the "nail in the coffin" that provides the conclusions formed during the preceding detective work with some scientific certainty. >Do all cases require CSIs? A: No, definitely not. Nowadays most drug cases as well as sexual assault cases will make use of forensic analysis. Murder cases can often make use of forensics, for trace analysis and/or firearms analysis, and possibly for DNA analysis. Driving while intoxicated cases depend on analysis for alcohol or drugs. Burglary cases *may* use forensics (for example to match the tools used to break in, with the marks they left behind at the crime scene, or DNA traces). But many other cases, such as domestic violence, simple assault, fraud, robbery, speeding tickets, streaking (just kidding - are you still paying attention?) - don't usually involve CSI types. >Do you sometimes turn to psychics to solve the case? Well, sometimes I think that's how my supervisor does his analyses.... I'm kidding again. I've never been involved in any case where psychics were brought in. I like to try to keep an open mind, but I suspect that most psychics are charlatans. Still, there are phenomena in the world that haven't been fully explained. >Do CSIs carry guns? A: Not in Texas state crime labs. I wouldn't trust some of the people with them, so I'm just as glad we don't. In some other states, they do (see below). >Are CSIs civilians? Field investigators too? Or do they carry badges? Is the situation the same across states? A: In some states, the crime lab analysts are sworn law enforcement officers - in a word, badge-carrying, gun-totin' police officers. That's true in Oklahoma, for example, and I think also in Colorado. In Texas and California, most of the crime lab analysts are *not* sworn police officers - they're civilians, so no badges other than our ID cards. Regarding field investigations, we do occasionally do these. The ones I have participated in involved so-called clandestine laboratories - illegal drug manufacturing labs. Here in Texas, it's illegal to sell/buy most chemical glassware without a state permit, so the labs usually made do with equipment improvised from pyrex mixing bowls, measuring cups, hot plates, etc. In California I don't think they have that restriction, right? So the CSI types there could see more sophisticated setups that might look more like a traditional chemistry lab. Still, by and large the crooks are *not* chemists - the recipes and techniques are passed around via the prison and criminal underground, so generally they don't really have any grasp of the science. (That's not always true - there was a case of a self-educated chemist in the Midwest that was making fentanyl in an old abandoned ICBM missile silo. He had to have quite a sophisticated setup, since the drug is some 10x stronger than heroin - fatal in sub-milligram amounts, and this guy was making kilograms of the stuff!) Their lack of knowledge is the reason a fair number of clandestine chemists end up dead; the ones that live often come down with strange cancers later in their lives. One common method for making methamphetamine uses red phosphorus - but a small change in the reaction conditions can also produce the deadly gas phosphine. There are books available that supposedly show you how to synthesize nerve gases - but *I* sure wouldn't want to try it in a clandestine lab setting - nor even in a well-equipped lab with fully functional fume hoods! >Do crime labs process their own evidence, or do they send it out to outside labs for processing? A: Usually, crime labs analyze their own evidence. There are some sorts of analyses that require specialized equipment that a particular lab may not have, so those would be sent to an outside lab. In Texas, for example, although there are 13 state crime labs total (the headquarters lab in Austin + 12 "field" labs scattered around the state), only the HQ lab has an XRD [X-ray diffraction] instrument. So if XRD analysis were needed, that evidence would be sent to the HQ lab. None of the state crime labs perform an analysis for marijuana in blood, so those cases (which are relatively few) are sent to private analytical labs. It's most common for crime labs to be able to analyze seized drugs, blood alcohol (from driving-while-intoxicated cases), trace evidence, fingerprints, and DNA and serology [though serology is becoming less common]. Many crime labs also do firearms/toolmarks testing and questioned documents analyses (hot checks, fraudulent securities, etc). Computer forensics is also becoming more common. In our lab system, computer forensics is part of the questioned documents lab (at HQ). The headquarters lab has sections that deal with all of the forensic subdisciplines, whereas individual field labs may only have a few of the specialties. Where I work, we only do drug analyses and blood alcohols. In El Paso, they have those plus DNA and firearms/ toolmarks sections. In Waco, they have drugs, blood alcohol, and DNA. In Tyler, there's drugs, blood alcohol, and firearms, but no DNA. In Amarillo, all they do is drug analyses. So it varies from lab to lab and state to state. Thanks for your questions! It's not often I get to talk at length about what I do to anyone outside the law enforcement/criminal justice community, so it's been a lot of fun to have the opportunity. I've been in the forensics field for 8.5 years now, and I was an analytical (quality control) chemist in industry for about 8 years before that. As far as schooling, oy vay I was an undergrad/grad chem. student for *far* too many years! LOL - Obviously I like chemistry - a lot! That has served me well in this job, because I go off on little tangents when something unusual comes across my bench to analyze. That's what helps keep the job interesting! -- Larry -- Sara: Would you like to have dinner with me? Grissom: (pause) No . Sara: Why not? Let's..let's have dinner..let's see what happens. Grissom: Sara..(sigh)..I don't know what to do about THIS. (gesturing towards them both) Sara:I do. You know by the time you figure it out,you really could be too late. -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 169.229.55.237