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尸体上的苍蝇能帮助解决谋杀案

The Flies on a Dead Body Can Help Solve a Murder

如果在野外发现了一具尸体 警察怀疑这跟谋杀有关
If a body is found in a field, and the cops suspect foul play is involved, establishing
那么确定准确的死亡时间至关重要
the exact time of death is critical.
判断出死者死亡时最后一刻的状态有利于调查人员
Figuring out the deceased’s final moments can help investigators corroborate people’s
证实人们的说法直到最终锁定杀手
stories to ultimately hone in on the killer.
但是 要怎么做呢?
But how do you do that?
当一个人死亡 有几种传统的方法可以对它进行判断
There are a few traditional ways to tell when someone died.
法医会检查尸体的温度 肤色 尸体僵硬的程度
Forensic examiners can measure body temperature, skin color, and degree of rigor mortis.
尸体开始分解时 上述所有都会发生变化 所以 了解这些变化处在哪个阶段
Each of these changes as the body begins decomposing, so knowing the stage of change they can work
他们可以逆向推断出死亡的时间
backwards to figure out the time of death.
然而 那些方法只适用于死亡后72小时内 超出这个时间
But all those methods only really work in the first 72 hours; any longer and those factors
那些因素已经被损坏 意味着发生了新的变化 这样就没有更多的数据可供收集
have piqued, meaning the changes have happened and there’s no more data to glean.
所以 当一具尸体超过3天的时间 调查人员就不得不使用
So, when a body has been a corpse for more than three days, investigators have to use
其他的方法来确定死亡的时间了 其中一种方法 就是研究
other methods to determine the time of death… one way is to look at all the different insects
以人的腐肉为生的各种昆虫
that feed on dead human flesh.
[恶心的声音]
*gross sound*
昆虫被正在分解的尸体释放出来气味和液体所吸引
Insects are drawn to the gasses and fluids released from a decomposing body; to them,
对于他们来说 这真是产卵和养育后代的肥沃土壤啊
it’s fertile ground to lay their eggs and cultivate their young.
[恶心的表情]到达尸体的第一种昆虫通常是丽蝇
*disgust face* The first insect to reach a corpse is usually a blowfly, which will lay
丽蝇会在人死后两天内将卵产于其中
eggs within two days of the person’s death.
食肉蝇也会在尸体分解过程的早期到来
Flesh flies also move in early in the decaying process.
尸体分解出来的脂肪吸引了白腹皮蠹和螟蛾
Decomposing body fat attracts hide beetles and pyralid moths.
随着时间的推移 肉体逐渐被分解 其他种类的蝇和有嘴巴能咀嚼更硬的食物的甲虫
As time go by and flesh breaks down, other species of flies and beetles that have mouths
也搬了进来 他们一起分享着这具尸体
to chew tougher food move in, consuming that dead flesh.
从那时起 这具尸体就变成了一个生态系统 这个生态系统里的昆虫以尸体为生
From there, the corpse becomes an ecosystem with insects feeding on the corpse also feeding
这些昆虫也互相各自为食
on each other.
这些听起来非常恶心却超级重要
This is all super gross but super important.
昆虫学家非常了解这些昆虫的生命周期 特别是
Entomologists know the life cycles of these insects, specifically the all-important blowfly
非常重要的 最先在尸体上产卵的丽蝇
that lays its eggs in the dead body first.
当要确定死亡时间的时候 他们就会研究丽蝇的发展阶段
When determining time of death, they can look at the stage of development of the blowfly
无论它是一个卵 一个幼体 一个蛹 或者是成年丽蝇 而且还要考虑到环境因素
— whether it’s an egg, larva, pupa, or adult — and take into account environmental
比如 热度和昆虫图案来逆向推断出 丽蝇产卵的大致时间
factors like heat and insect patterns to work backwards and figure out approximately when
这样就可以知道死亡时间
the blowfly laid its eggs, which can tell them the time of death.
这个我们很擅长 但有一个问题 我们得精确地知道
We’re really good at this, but there’s a problem… we need to know exactly what
那个幼体属于哪个物种
species that larva is.
它们看起来都差不多
And they all sort of look alike.
法医需要知道生物的种类以便更好的估计死者的发展时间
The examiner needs to know the species for a better estimation of development time and
和死亡时间
time of death.
他们可以对卵做基因检测 但那非常昂贵
They can do a DNA test on an egg, but that can be pricey.
更廉价的方式是收集卵 在实验室里让它发育成熟
The cheaper option is to collect the egg and let it grow to adulthood in a lab to figure
来判断种类 然后从那时逆向推断
out the species, and work backwards from there.
当然 如果你要尝试找出谁杀了人 然后把尸体丢弃在野外的话
Of course, if you’re trying to find out who killed someone and left them in a field…
等上三天左右的时间 让一个蝇卵变成羽翼丰满的昆虫 这是令人焦急的
waiting three or so days for a fly egg to become a fully-formed insect is stressful.
那时 罪犯早就逃亡另一个国家了
A criminal can flee to a new country by then!
了解到卵的身份是一个大问题 一位有机化学家和一位
Knowing the egg-identification thing is an issue, an organic chemist teamed up with a
法医昆虫学家一起合作对丽蝇卵实施了实时质谱分析
forensic entomologist to apply real-time mass spectrometry to blowfly eggs.
这对于法医学来说可能是一场革命
And it could be a game changer to forensic science.
在革命到来之前 他们需要了解所有蝇类的种类
Before we get to that though, they had to learn about all these species of flies.
为了实现这个目标 研究人员把猪肝放进了捕捉器里 隐藏在曼哈顿城市周围
To do that, the researchers put pork liver in traps hidden around Manhattan.
这不是伪科学
This is real science.
它们吸引了四种丽蝇 并且在它们产卵前把它们捕捉到
They attracted four species of blowfly, and trapped them before they laid their eggs.
他们确定了丽蝇的种类 然后把它们放在新鲜的猪肝上产卵
They determined their species and then put them on a fresh liver to seed with their spawn.
通过那种方法 他们知道了哪种丽蝇在哪里产卵
That way they knew what species were laying eggs where.
然后 他们把这些卵收集起来 通过质谱分析法对各个卵进行试验 得到它们的化学指纹图
Then they collected the eggs and tested each in a mass spectrometer to get a chemical fingerprint.
质谱分析法解释起来很复杂 基本上是这样:样本被电离
Mass spectrometry is really complicated to explain, but basically: a sample is ionized,
原子根据质量和电荷被分类 然后可以得到一幅看起来是这样的图形
the atoms are sorted by mass and charge and it gives you a graph that looks like this.
通过这个 我们可以判断出某物是由什么原子构成的 也就是他们说的化学指纹图
With this we can figure out what atoms something is made of, what they call the chemical fingerprint.
由于所有物质都是由原子构成的 那我们就可以把这个技术应用到
And since everything is made of atoms, we can apply this technology to things like uncovering
类似发现丽蝇卵氨基酸的事情上
the amino acids in blowfly eggs!
弄清楚了种类后就分析卵
Knowing the species then analyzing the eggs
这给予了他们第一种以化学为基础的分辨丽蝇卵的方法
gave them the first ever chemically-based
而且这只需要几分钟的时间就能完成
way to identify blowfly eggs, and it only takes minutes to do it!
理想的情况下 如果这个技术可行的话 昆虫学家可以利用来自犯罪现场的所有数据
Ideally, if this tech works, entomologists can use all the data from the crime scene
对蝇幼体实施快速的质谱分析试验 就可以 找到死者死亡的大致时间
and a quick mass spectrometry check of the fly larvae to find an approximate time of death.
但是 仅凭这一点还不足以逮捕罪犯
But, we can’t use this to catch criminals yet.
科学家还需要检测更多种类蝇的化学特征
Scientists will need to measure the chemical signature of more species, and then create
然后建立一个数据库 未知卵的光谱与数据库可以进行比对 这样确保
a database against which spectra of unknown eggs can be compared.This promises to advance
推动了法医昆虫学的发展 由此引申开来 当在野外遇到一具尸体时
forensic entomology, and by extension help investigators act quickly when faced with
调查人员也可以迅速行动起来
a dead body in a field.
但 如果说野外的尸体无人发现 直到它被昆虫全部吃得干干净净
But let’s say no one found the body in the field until it was picked clean by insects…
那法医就只能仅仅从一块头盖骨来判断事情的发生经过了
then forensic examiners have to figure out what happened using just a skull!
这一节的视频就讲到这里
I talk about that in this episode right here.
在这个视频里 你有没有做到不反胃呢?
Did you make it through this video without vomiting?
我好像没有做到
I almost didn’t.
通过评论 让我们知道你的想法吧 订阅我们的视频 回来发现Seeker上更多的视频
Let us know your thoughts in the comments, subscribe and come back here for more Seeker

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视频概述

有关刑事侦查的技术普及视频,整个视频有点儿恶心单很实用哦

听录译者

收集自网络

翻译译者

Vincent

审核员

审核团C

视频来源

https://www.youtube.com/watch?v=Ny_YHf6lmtc

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