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Think about what you were doing between the years 1985 and 2009.
想想1985年到2009年间你在做什么。
All those years you spent getting your education, building a resume.
那些年你都在忙着接受教育，忙着准备简历。
"Mr. Gorbachev, tear down that wall."
“戈尔巴乔夫先生，推倒了那堵墙。”
Getting married. Buying a home.
忙着结婚。买房。
"The Hubble Space Telescope is released."
“哈勃太空望远镜发射了。”
Having children.
以及忙着生孩子。
"Can you explain what internet is?"
“你能解释一下什么是互联网吗？”
Building up retirement.
忙着准备退休。
"O.J.Simpson not guilty of the crime."
“O.J.辛普森无罪。”
Watching your children grow up. Funerals of your family members and your loved ones.
你的孩子逐渐长大成人。你的家人和亲人也一个接一个离开了人世。
I mean it's just an enormous amount of time.
这可是一段非常漫长的时间啊。
You come out and how are you supposed to explain, 'Well I was convicted of murder but I didn't do it.' That baggage stays with you, forever."
那些年都在监狱里的你走出来之后，你应该怎么去跟大家解释，‘我被判了谋杀罪，但我没有杀人。’这个问题，这个思想包袱会跟着你，永远地跟着你。”
Robert Lee Stinson was convicted of murder on the basis of forensic bite mark evidence.
根据法医咬痕证据，罗伯特·李·斯廷森被判了谋杀罪。
He refused to admit guilt, so he was never granted parole.
他拒绝认罪，所以他从未得到过假释。
By 2003, he'd been in prison for 18 years.
到2003年为止，他已经在监狱里呆了18年。
That's when when he wrote to the Innocence Project at the University of Wisconsin.
也就是在那一年，他写信给威斯康辛大学的“无罪计划”。
"It was a request for assistance saying that he was innocent and that he was convicted on bite mark evidence.
“那是一封求助信，他在信中说自己是无辜的，而且他是根据咬痕证据被定罪的。”
They took the bite mark evidence out of storage and sent it to four forensic odontologists to review.
他们把咬痕证据从仓库里拿出来，送给四名法医牙医学专家检查。
And they found that the dentists who testified against Stinson, L. T. Johnson and Raymond Rawson,
专家们发现，指证斯廷森的牙医约翰逊和雷蒙德·劳森医生
had made a "series of errors that resulted in an incorrect determination."
犯了“一系列错误，最终导致了对斯廷森错误的判决”。
They said Johnson's technique of placing a semi-opaque overlay on top of the bite marks obscured the fact that they didn't match.
他们说，约翰逊使用的，在咬痕上涂半透明涂层的技术掩盖了两者不匹配的事实。
And they showed how misleading it could be to hold a dental model up to a bite mark impression, which Johnson had done in front of the jury.
专家们还展示了用牙齿模型来和咬痕痕迹作比对，这恰好是约翰逊在陪审团面前演示的操作，多具误导性。
It makes it look like Stinson's teeth fit, but it also looks like these three random sets of teeth fit too.
这种技术让斯廷森的牙齿看似跟死者身上的咬痕一致，但也会让这三组任意取来的牙齿模型有同样效果。
Overall, they concluded that "Stinson can be excluded from" having made the bite marks.
总之，专家们得出的结论是，“斯廷森可以被排除在”留下咬痕的疑犯人选之外。
"We said look, it's not him. And the prosecutors looked at it and they said we gotta talk to Dr. Johnson
我们说，看，不是他。检察官看了之后说我们得和约翰逊医生谈谈，
and they came back and they said, no we stand by it. It's him.
之后他们回来说，不，我们还是坚持原判。凶手就是他。
Where? how can you see that? But they did."
哪里是他了？你们怎么看出来是他的？但他们就是那么说的。”
Fortunately, the bite marks weren't the only physical evidence in the case anymore.
幸运的是，咬痕不再是案件中唯一的物理证据了。
The same day Stinson was convicted, December 12th, 1985,
就是1985年12月12日，也就是斯廷森被定罪的那天，
a paper was published in the journal Nature reporting that DNA could be used in forensics.
一篇发表在《自然》杂志上的论文称，DNA可用于法医鉴定了。
"It is evidence that promises a breakthrough future for law enforcement officials."
“这一论文表明执法官员取得法医鉴定方面的突破已经指日可待。”
"These genetic fingerprints are a powerful tool for solving mysterious crimes."
“这些基因指纹堪称是破案的有力工具。”
We know today that DNA is a powerful form of evidence, but it's worth digging into why that is.
如今，我们知道DNA是一种强有力的证据，但我们有必要深入研究它为什么强有力的原因。
In our cells, there's a small section where a short DNA phrase gets repeated several times.
在我们的细胞中，有一个小段DNA片段被重复多次的地方。
We all have it in the same location, but the number of repeats varies between people.
我们所有人细胞中的这个地方的位置都是想同的，但DNA重复的次数因人而异。
I might have 9. You might have 15.
我的细胞重复的次数可能是9。你的次数可能是15次。
We have instruments that can essentially count the repeats by their size.
我们有仪器可以根据它们的大小来计算重复的次数。
And because we can count them, we can survey a bunch of people to see how common each number is.
因为我们能算出重复的次数，所以我们可以对一群人展开调查，看每个数字有多普遍。
So let's say police find a DNA sample with 9 repeats.
假设警察发现了一个DNA样本的重复次数为9次。
Well, if 30% of people have 9 repeats, that's not very strong evidence.
那么，如果30%的人重复的次数都是9次，这就算不上很有力的证据。
But scientists have identified more than 13 different locations on our DNA where we vary in these kinds of repeats.
但是科学家们已经在我们的DNA上识别出了13个不同的位置，在这些位置上我们的重复次数都是不同的。
And we have two numbers for each location because we inherit one from each parent.
而且，每个位置都有两个数字，因为我们从父母双方各继承了一个数字。
So maybe I have 9,9 at one location; 14,16 at another; 12,10 at a third, and so on.
所以，我的DNA上某个位置的数字可能是9，9;另一个位置的是14,16；第三个位置的则是12，以此类推。
