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为什么我们不能依赖DNA证据? – 译学馆
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为什么我们不能依赖DNA证据?

Why We Can’t Always Trust DNA Evidence

DNA是双螺旋结构 所以我猜你会说它是
DNA is a double-helix, so I guess you could say that DNA was
被弯成这个形状的
bent into shape.
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Trace here for DNews.
DNA证据常被看作犯罪现场调查中的绝招
DNA evidence is often seen as the silver bullet of crime scene investigations…
只需要极少的血
start with a tiny dab of blood,
很短的时间 凶徒就会被绳之以法
add a 10 second lab montage, and the perp is behind bars.
是这样吗 不完全是
Right? Not much.
DNA分析的确很强大
As powerful as DNA analysis is,
但它也并不像大众和法院所说的
it’s not the perfect evidence that the general public,
“完美的证据”
and the court system, make it out to be.
首先 来看看它的历史
First, a little background.
DNA识别技术源于1984年
DNA fingerprinting was developed back in 1984,
当时就已经研究出了关于基因的一些基本原理
and it exploits some basic truths about genetics.
DNA由四个基本化学元素组成
All DNA is comprised of four chemical bases:
腺嘌呤 胞嘧啶 鸟嘌呤 胸腺嘧啶
Adenine, Cytosine, Guanine, and Thymine.
这些连接在一起形成碱基对
These link together to form base pairs,
碱基对长链连接起来形成DNA链
and long chains of base pairs link up to form strands of DNA.
碱基对的不同组合导致基因差异
Different combinations of those base pairs define different genes,
进而导致性状差异
and thus different traits.
总的来说 人类基因组包含约30亿碱基对
In total, the human genome contains about 3 billion base pairs…
但仅有约0.1%体现在个体差异中
but only about point one percent of those vary from person to person,
这仅有的0.1%让每个人都独一无二
and that tiny slice of the pie accounts for everyone’s unique traits.
DNA识别技术就利用了这0.1%的差异
And it’s that 0.1% that DNA fingerprinting utilizes.
在犯罪现场找到血液 唾液样本或其他“遗留物”后
When samples of blood, saliva, or other “leavings” are found at a crime scene,
专家分析这些样本中的DNA片段
experts analyze the DNA fragments within those samples
然后比对嫌疑人DNA
and compare them to a suspect’s DNA…
或者比对罪犯记录数据库
or to a database of people with criminal records.
找到的碱基对越独特
The more distinct sets of base pairs you can find,
能匹配或划去的样本就越多
the more confidently you can match, or rule out, samples.
1984年之后 这一程序更快捷便宜也更精准
Since 1984 this procedure has gotten quicker, cheaper,
因此被频繁投入使用
and more accurate, and has exploded in use.
但也存在问题
But here’s the problem:
虽然DNA测验有用
as useful as DNA testing is,
但它不像CSI那样
it’s not necessarily the forensic turn-key solution
是法庭证物的必需品
that shows like CSI make it out to be.
很大程度上是因为收集和分析DNA的过程
And that’s largely because the process of collecting and analyzing DNA
极具争议
can be surprisingly ambiguous.
首先 哪都有DNA
First off, DNA is everywhere.
一小部分皮肤 唾液 血液
Tiny traces of skin, saliva, blood
或者其他含DNA的证物
or other DNA-containing material are often found
在犯罪现场到处都能找到
all over a crime scene,
收集样本技术含量低 耗时 易错
and collecting samples is low-tech, time-consuming, and fairly error-prone.
一旦发现样本 研究员要找出
Once samples are in, investigators must figure out
哪个是和罪犯有关的样本
which are relevant to the crime…
这是个大工程
it’s just no small task.
更糟的是 罪犯的DNA常和受害人的在一起
Worse, DNA from the perp is often mixed with that of the victim,
需要实验室技术梳理区分
requiring lab techs to tease out which is which.
总之 DNA证据常被弄混
All in all, DNA evidence is frequently messy,
需要专家尝试和推断
requiring experts to try and extrapolate
一个不完整的或混乱的DNA片段能否和参考样本匹配
whether an incomplete or mixed DNA profile truly matches a reference sample.
有点像试着找出
It’s sort of like trying to figure out
一些杂乱的碎片是否和盒子上的图片对应
whether a few scattered puzzle pieces even belong
更不用说拼在一起了
to the picture on the box, let alone fit together.
这一混乱可能导致实验室判断错误
This ambiguity can lead to labs fudging results
帮不到研究员 或基因分析错误 或完全错误
to help out investigators, or genuine errors in analysis, or outright fraud.
这一切错误都源于基因匹配的错误
And all that opens the door for false positives in DNA matches.
悲哀的是 滥用DNA证据致死有多例
Sadly, there are many examples of misused DNA evidence ruining lives.
1998年约西亚·萨顿因强奸女人
In 1998 Josiah Sutton was arrested
在休斯顿的德克萨斯州被捕
and charged with raping a woman in Houston, Texas.
一个罪犯实验员在实验中证明
A crime lab employee testified at the trial that
休斯顿和犯罪现场获取DNA完全匹配
Sutton was an “exact match” with the DNA recovered from the scene.
他被定罪 在第二次实验证明
He was convicted, and spent almost five years in prison
他不是“准确匹配”之前
before a second round of testing
他在监狱呆了五年
found he was in no way an “exact match.”
第二次测试没有使用任何新证据
That second test didn’t make use of any new evidence…
只是对DNA的理解更加精准
it simply interpreted the DNA more accurately.
下例中 混合的DNA浪费了宝贵的时间和金钱
And then there’s DNA mixups wasting valuable time and money.
欧洲研究员寻找“海尔布隆幽灵”超过15年
For more than 15 years, investigators in Europe searched for the Phantom of Heilbronn,
“海尔布隆幽灵”是一个在整个欧洲大陆
a criminal mastermind who left identical DNA traces
超过40个犯罪现场留下DNA遗迹的“惯犯”
at more than 40 crime scenes across the continent.
在一次详尽的调查之后
After an exhaustive manhunt,
嫌疑DNA最终匹配到了
the DNA in question was finally matched…
一个做DNA检验棉签的帮工身上
to a factory worker who helped make DNA test kits.
所以 看 我们不是争辩
So, look.We’re NOT arguing that,
“因为有些人不会用 DNA证据才不好用”
“DNA evidence doesn’t work because some people don’t use it right.”
DNA识别技术彻底改变了法医学
DNA fingerprinting has revolutionized forensics,
至今 单单美国就有
and to date has exonerated 347 wrongfully-convicted
347起错判翻案
people in the US alone.
也有人认为DNA测验
But there is a perception that DNA testing
简单且绝无错误
is both simple and infallible.
陪审员就有过于依赖物证的倾向
Jurors tend to overcommit to physical evidence
特别是专家提供的物证
when it’s presented as fact by experts.
研究员提出了“CSI影响”
Researchers have even proposed a “CSI Effect,”
即陪审员趋向于认为每次审讯中
which is the tendency of juries expect
DNA证据又快又准
fast and conclusive DNA evidence in every trial.
和科学一样 DNA证据也有危险趋势
These are dangerous trends because, as sound as the science is,
除非在允许范围内使用 否则对谁都不好
it’s no good to anyone unless it’s used within its limits.
像任何科学一样
Like any science.
如果你想了解更多
If you’d like to learn more about DNA,
除了本视频我们还有关于
check out this video we have on CRISPR
可以编辑DNA的CRISPR技术视频
which could actually edit your DNA.
如果你有关于法医学的其他问题
What other questions do you have about forensic science?
在评论中告诉我们
Let us know down in the comments,
确定你订阅了DNews 谢谢观看
make sure you subscribe for DNews and thanks for watching.

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视频概述

2017年《犯罪心理:穿越国界》第二季中,DNA对寻找线索有极大的帮助,那么通过DNA得到的推断就一定正确吗?

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收集自网络

翻译译者

岸雩

审核员

审核团H

视频来源

https://www.youtube.com/watch?v=601U11FH6iE

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