2014年经济学人 手机数据的滥用 两个发射塔

The abuse of mobile-phone data

The two towers

Junk science is putting innocent people in jail

SOMEONE strangled a prostitute in Portland, Oregon in 2002. The police arrested Lisa Roberts, the victim's ex-lover, who spent more than two years in custody¹ awaiting trial. Shortly before the trial the prosecutor² told Ms Roberts, via her lawyer, that tower data collected by Verizon, her mobile-telephone network, showed precisely³ where she was at the time of the murder. As her lawyer recalled, the prosecutor said Ms Roberts could be “pinpointed” in a park shortly before the victim's naked and sexually assaulted corpse⁴ was found there. She was told she faced 25 years to life in prison. She accepted a deal to plead guilty and serve 15 years.

But the high-tech⁵ evidence against her was bunk⁶. Routinely collected tower data can place a mobile phone in a broad area, but it cannot “pinpoint” it. That would require a special three-tower “triangulation”, which cannot reveal past locations. It took a decade for Ms Roberts's guilty plea to be thrown out. On May 28th she left prison, her criminal record clean, after nearly 12 years in custody.

Mobile-phone-tower location data is widely used in court, says Steven Jansen of the Association of Prosecuting⁷ Attorneys in Washington, DC. Last year America's courts and law-enforcement agencies served 37,839 subpoenas⁸, court orders, and search warrants for location data just to one phone company, AT&T. This year's figure had already climbed to 30,886 by the end of June, the company says.

In the past couple of years defence lawyers have brought in more experts to challenge tower evidence, says Mr Jansen. Most police officers and lawyers have “no clue” how phone networks function, says Ryan Bialas, a North Dakota public defender⁹. Cop shows like “CSI” give juries the idea that scientific evidence is almost infallible. But tower data is far less accurate than prosecutors¹⁰ sometimes claim.

Location, location, location

Cherry Biometrics, a Virginia forensics firm, has testified in more than 20 trials where tower evidence was being used. In all of them, says Michael Cherry, the boss, prosecutors misunderstood the technology. Often they would assert that mobile phones connect to the nearest tower. In fact, two calls dialled consecutively¹¹ from the same spot may connect to two different towers: one close by, the other many miles away. Defence lawyers sometimes use the same “junk science” to support alibis¹², adds Mr Cherry.

The tower cited in Ms Roberts's case could have handled calls from as far as 20 miles (32km) away, according to a deposition¹³ prepared by Cherry Biometrics. Which tower a phone connects with depends on such factors as how thick the nearby foliage¹⁴ and walls are, the size of nearby cars and bodies of water, and how well the handset is working. None of this information is usually recorded.

Without it, much of the tower evidence presented in court is useless, writes Larry Daniel of Guardian¹⁵ Digital Forensics in a forthcoming book on the subject. Mr Daniel has found errors in nearly half of the 240 consulting jobs he has done for prosecutors and defence lawyers. Even so, tower records do have a place in court, says Mr Daniel: they can generally prove that a handset has moved between broad areas such as non-adjacent cities.

Preventing the misuse¹⁶ of tower data should not be hard, though it can be expensive. Guardian Digital Forensics charges $250 an hour for its expertise¹⁷. The judge who freed Ms Roberts faulted her lawyer, now dead, for failing to challenge mobile-phone evidence that would probably have collapsed¹⁸ before a jury. William Teesdale, the chief investigator¹⁹ for Portland's federal defender's office, complains that the prosecutor, Rod Underhill, never addressed another call on Ms Roberts's phone around the same time as the one that supposedly placed her at the murder scene. It connected to a different tower, farther away from the park and closer to a spot where Ms Roberts had been seen by a witness. Mr Underhill refused to comment.

1 custody   

n.监护，照看，羁押，拘留

参考例句：

• He spent a week in custody on remand awaiting sentence.等候判决期间他被还押候审一个星期。
• He was taken into custody immediately after the robbery.抢劫案发生后，他立即被押了起来。

2 prosecutor   

n.起诉人；检察官，公诉人

参考例句：

• The defender argued down the prosecutor at the court.辩护人在法庭上驳倒了起诉人。
• The prosecutor would tear your testimony to pieces.检查官会把你的证言驳得体无完肤。

3 precisely   

adv.恰好，正好，精确地，细致地

参考例句：

• It's precisely that sort of slick sales-talk that I mistrust.我不相信的正是那种油腔滑调的推销宣传。
• The man adjusted very precisely.那个人调得很准。

4 corpse   

n.尸体，死尸

参考例句：

• What she saw was just an unfeeling corpse.她见到的只是一具全无感觉的尸体。
• The corpse was preserved from decay by embalming.尸体用香料涂抹以防腐烂。

5 high-tech   

adj.高科技的

参考例句：

• The economy is in the upswing which makes high-tech services in more demand too.经济在蓬勃发展，这就使对高科技服务的需求量也在加大。
• The quest of a cure for disease with high-tech has never ceased. 人们希望运用高科技治疗疾病的追求从未停止过。

6 bunk   

n.(车、船等倚壁而设的)铺位；废话

参考例句：

• He left his bunk and went up on deck again.他离开自己的铺位再次走到甲板上。
• Most economists think his theories are sheer bunk.大多数经济学家认为他的理论纯属胡说。

7 prosecuting   

检举、告发某人( prosecute的现在分词 )； 对某人提起公诉； 继续从事（某事物）； 担任控方律师

参考例句：

• The witness was cross-examined by the prosecuting counsel. 证人接受控方律师的盘问。
• Every point made by the prosecuting attorney was telling. 检查官提出的每一点都是有力的。

8 subpoenas   

n.（传唤出庭的）传票( subpoena的名词复数 )v.（用传票）传唤（某人）( subpoena的第三人称单数 )

参考例句：

• My company has complied with committee subpoenas by supplying documents confirming all that I have said. 本公司按照委员会的要求，提供了能够证实我刚才发言的文件。 来自辞典例句
• Congressional Investigations: Subpoenas and Contempt Power. Report for Congress April 2, 2003. 金灿荣：《美国国会的监督功能》，载《教学与研究》2003年第2期。 来自互联网

9 defender   

n.保卫者，拥护者，辩护人

参考例句：

• He shouldered off a defender and shot at goal.他用肩膀挡开防守队员，然后射门。
• The defender argued down the prosecutor at the court.辩护人在法庭上驳倒了起诉人。

10 prosecutors   

检举人( prosecutor的名词复数 )； 告发人； 起诉人； 公诉人

参考例句：

• In some places,public prosecutors are elected rather than appointed. 在有些地方，检察官是经选举而非任命产生的。 来自口语例句
• You've been summoned to the Prosecutors' Office, 2 days later. 你在两天以后被宣到了检察官的办公室。

11 consecutively   

adv.连续地

参考例句：

• He was actually too depleted to think consecutively about anything. 他已经打不起一点精神，根本谈不上好好思考一下。 来自辞典例句
• In any game, the right to serve shall pass consecutively. 在一局中，不错的发球挨次应该是。 来自互联网

12 alibis   

某人在别处的证据( alibi的名词复数 )； 不在犯罪现场的证人； 借口； 托辞

参考例句：

• The suspects all had alibis for the day of the robbery. 嫌疑人均有证据证明抢劫当天不在犯罪现场。
• I'm not trying to beat your alibis any more than I'm trying to prove 'em. 我并不是不让你辩护，我只是想把那个人找出来。

13 deposition   

n.免职，罢官；作证；沉淀；沉淀物

参考例句：

• It was this issue which led to the deposition of the king.正是这件事导致了国王被废黜。
• This leads to calcium deposition in the blood-vessels.这导致钙在血管中沉积。

14 foliage   

n.叶子，树叶，簇叶

参考例句：

• The path was completely covered by the dense foliage.小路被树叶厚厚地盖了一层。
• Dark foliage clothes the hills.浓密的树叶覆盖着群山。

15 guardian   

n.监护人；守卫者，保护者

参考例句：

• The form must be signed by the child's parents or guardian. 这张表格须由孩子的家长或监护人签字。
• The press is a guardian of the public weal. 报刊是公共福利的卫护者。

16 misuse   

n.误用，滥用；vt.误用，滥用

参考例句：

• It disturbs me profoundly that you so misuse your talents.你如此滥用自己的才能，使我深感不安。
• He was sacked for computer misuse.他因滥用计算机而被解雇了。

17 expertise   

n.专门知识(或技能等)，专长

参考例句：

• We were amazed at his expertise on the ski slopes.他斜坡滑雪的技能使我们赞叹不已。
• You really have the technical expertise in a new breakthrough.让你真正在专业技术上有一个全新的突破。

18 collapsed   

adj.倒塌的

参考例句：

• Jack collapsed in agony on the floor. 杰克十分痛苦地瘫倒在地板上。
• The roof collapsed under the weight of snow. 房顶在雪的重压下突然坍塌下来。

19 investigator   

n.研究者，调查者，审查者

参考例句：

• He was a special investigator for the FBI.他是联邦调查局的特别调查员。
• The investigator was able to deduce the crime and find the criminal.调查者能够推出犯罪过程并锁定罪犯。