经济学人下载:司法鉴定(1)

Since the first use of fingerprints to identify and convict a murderer, in 1892,
自从1892年首次使用指纹来识别并定罪谋杀犯以来，

detectives the world over have come to rely heavily on print evidence to build their cases against suspects.
世界各地的侦探都开始严重依赖指纹证据来建立针对嫌疑人的案件。

One limit on the value of fingerprints, though, is that it is hard to work out how old they are.
然而，指纹价值的一个限制是很难计算出它们的年代。

This is a particular problem when a crime is committed somewhere
当犯罪发生在犯罪嫌疑人经常且正当出入的场所，如工作地时，

that a suspect frequently and legitimately visits, such as a place of work.
这个问题就特别的突出。

In this case exactly when a print was made might be crucial to establishing guilt or innocence.
在这种情况下，准确的指纹时间可能是确定有罪或无罪的关键。

But it is information that science has, until now,been unable to provide with any accuracy.
但是直到现在，科学还不能提供任何准确的信息。

As they write in Analytical Chemistry, Paige Hinners and Young Jin Lee of Iowa State University
正如他们在《As they write in Analytical Chemistry》所写的那样，爱荷华州立大学的

believe they can remedy this state of affairs. They knew from work conducted by other laboratories
Paige Hinners和Young Jin Lee认为他们可以改变这种状况。他们从其他实验的工作中了解到

that the triglyceride oils contained in fingerprints change by oxidation over the course of time.
指纹中所含的甘油三脂油会随着时间的推移而氧化。

That provides an obvious way to date prints.
这为推算指纹时间提供了一种明显的方法。

The problem is that the techniques which have been applied to analyse these oils are able to distinguish age only crudely.
问题是用来分析这些油的技术只能粗略地分辨出年代。

In practice, they can determine whether or not a print is over a week old, but nothing else.
在实践中，他们可以确定一个指纹是否已经超过一周了，但除此之外别无其他。

Dr Hinners and Dr Lee wondered if higher precision could be obtained by thinking a bit more about oxidation.
Hinners博士和Lee博士想知道更高的精确度是否可以通过更多地考虑氧化来获得。

Oxygen molecules in the air come in two varieties. Most have a pair of atoms but some, known as ozone, have three.
空气中的氧分子有两种，大多数都有一对原子，但也有一些被称为臭氧的有三个原子。

Though far rarer than diatomic oxygen, ozone is more reactive and also reacts in ways different from those of its two-atomed cousin.
尽管臭氧比双原子氧更加稀有，但它的反应性更强，而且反应方式也与双原子氧不同。

The two researchers therefore decided to focus their attentions on ozonolysis, as triatomic oxidation is known.
因此，这两位研究人员决定将他们的研究重点放在臭氧（即三原子氧化）的分解上。

Triglycerides, as their name suggests, are three-tailed molecules.
甘油三脂，顾名思义，是三尾分子。

Each tail is a chain of carbon atoms, with hydrogen atoms bonded to the carbons.
每条尾巴都是一个碳原子链，氢原子连着碳原子。