Scott Fraser: The problem with eyewitness testimony

Translator: Joseph Geni Reviewer: Morton Bast

譯者: Barry Hu 審譯者: NAN-KUN WU

The murder happened a little over 21 years ago,

一件大約發生21年多前的謀殺，

January the 18th, 1991,

1991年1月18日

in a small

有個小小的

bedroom community

住宅區

of Lynwood, California, just a few miles

加州林伍市,位於洛杉磯(Los Angeles)

southeast of Los Angeles.

沒幾里的西南郊外

A father came out of his house

一個父親步出自家大門

to tell his teenage son and his five friends

告訴他十幾歲的兒子及五個朋友

that it was time for them to stop horsing around

別再在門前和人行道玩鬧了，

on the front lawn and on the sidewalk,

別再在門前和人行道玩鬧了，

to get home, finish their schoolwork,

該回家寫功課，

and prepare themselves for bed.

準備睡覺了

And as the father was administering these instructions,

就在說這些話的時候

a car drove by, slowly,

一部車緩緩駛過，

and just after it passed the father and the teenagers,

車子經過父親和這些孩子們身邊，

a hand went out from the front passenger window,

有隻手從前座乘客邊窗口伸出來，

and -- "Bam, Bam!" -- killing the father.

然後 「砰，砰」兩聲槍響，殺了那位父親。

And the car sped off.

車子隨即疾駛而去

The police,

警方

investigating officers, were amazingly efficient.

負責調查的員警，超有效率

They considered all the usual culprits,

他們就當地不良分子裡，

and in less than 24 hours, they had selected their suspect:

不到24小時，就挑出了嫌犯︰

Francisco Carrillo, a 17-year-old kid

佛藍西司科．卡瑞羅(Francisco Carrillo)，一個17歲大的小伙子

who lived about two or three blocks away

他家離槍擊現場

from where the shooting occurred.

不過2、3個巷子

They found photos of him. They prepared a photo array,

警方拿他的照片，準備照片指認。

and the day after the shooting,

案發隔天，

they showed it to one of the teenagers, and he said,

拿給案發現場的青少年之一指認，他說：

"That's the picture.

「就是這照片上的人！」

That's the shooter I saw that killed the father."

「這就是我看到的殺了我朋友父親的槍手！」

That was all a preliminary hearing judge had

審前指控聽證庭的法官就憑這句話

to listen to, to bind Mr. Carrillo over to stand trial

判定卡瑞羅先生應受審判

for a first-degree murder.

罪名為一級謀殺。

In the investigation that followed before the actual trial,

正式庭審前的偵查裡，

each of the other five teenagers was shown

在場的五個青少年都看了同一組照片。

photographs, the same photo array.

在場的五個青少年都看了同一組照片。

The picture that we best can determine was probably

這組大頭照裡,你們看到的左下角那張,最可能就是警方放進指認照片組那張

the one that they were shown in the photo array

這組大頭照裡,你們看到的左下角那張,最可能就是警方放進指認照片組那張

is in your bottom left hand corner of these mug shots.

這組大頭照裡,你們看到的左下角那張,最可能就是警方放進指認照片組那張

The reason we're not sure absolutely is because

我們之所以無法絕對肯定

of the nature of evidence preservation

源自於我們司法體系

in our judicial system,

保存證據的方式，

but that's another whole TEDx talk for later. (Laughter)

但這可以是日後另一個TEDx 演說題目。（笑聲）

So at the actual trial,

實際審判的時候

all six of the teenagers testified,

6個孩子都上台作證，

and indicated the identifications they had made

並由指認相片中指出兇嫌。

in the photo array.

並由指認相片中指出兇嫌。

He was convicted. He was sentenced to life imprisonment,

卡瑞羅先生被定罪，被判終身監禁

and transported to Folsom Prison.

並送到佛森(Folsom)監獄服刑。

So what's wrong?

有問題嗎？

Straightforward, fair trial, full investigation.

一切直截了當，公平審判，完整的調查。

Oh yes, no gun was ever found.

對了，沒找到凶槍。

No vehicle was ever identified as being the one

沒找到那輛手伸出窗外的兇車，

in which the shooter had extended his arm,

沒找到那輛手伸出窗外的兇車，

and no person was ever charged with being the driver

也沒找到兇車的駕駛。

of the shooter's vehicle.

也沒找到兇車的駕駛。

And Mr. Carrillo's alibi?

至於卡瑞羅先生的不在場證明呢？

Which of those parents here in the room might not lie

你們當中哪一位身為父母的

concerning the whereabouts of your son or daughter

在涉嫌凶殺案件的調查中

in an investigation of a killing?

不會為兒女案發當時行蹤說謊？

Sent to prison,

他被送到監獄服刑

adamantly insisting on his innocence,

一直強烈堅持自己無辜

which he has consistently for 21 years.

一直堅持了21年

So what's the problem?

怎麼回事？

The problems, actually, for this kind of case

這個問題，實際上，這類型的案件，

come manyfold from decades of scientific research

有問題都是因為數十年來的科學研究

involving human memory.

關於人類記憶的研究的挑戰。

First of all, we have all the statistical analyses

首先，我們有詳盡的統計資料

from the Innocence Project work,

來自「拯救錯判」計畫(Innocence Project)

where we know that we have, what,

從中，我們記錄了，多少件？

250, 280 documented cases now where people have

25萬又280件案件，都是錯誤判決

been wrongfully convicted and subsequently exonerated,

而在事後被平反的案件，

some from death row, on the basis of later DNA analysis,

有些人由於後續的DNA證據，自死刑邊緣被救回

and you know that over three quarters of all of those cases

而我們發現，所有翻案案件，有四分之三，

of exoneration involved only eyewitness identification

在受審時僅是根據目擊者的指證

testimony during the trial that convicted them.

就遭定罪。

We know that eyewitness identifications are fallible.

我們知道目擊者的指證並不可靠。

The other comes from an interesting aspect

其他（非DNA）都來自於

of human memory that's related to various brain functions

和不同大腦的功能都有關 ，但相關記憶的一個有趣面向

but I can sum up for the sake of brevity here

但為了簡潔起見，

in a simple line:

我可以用一句話來概括 -

The brain abhors a vacuum.

「腦子痛恨空白」

Under the best of observation conditions,

最棒的觀察條件下

the absolute best,

絕對的最清晰狀況

we only detect, encode and store in our brains

我們對眼前的經歷經察覺，編排，然後記錄在大腦裡的

bits and pieces of the entire experience in front of us,

只有支離破碎的片段，

and they're stored in different parts of the brain.

而這些片段儲存在大腦中不同部位。

So now, when it's important for us to be able to recall

所以，當我們必須要回憶

what it was that we experienced,

我們所經歷的事件時，

we have an incomplete, we have a partial store,

我們記得並不完全， 我們只記得一部份，

and what happens?

然後呢？

Below awareness, with no requirement for any kind of

不知不覺地，不必有任何動機

motivated processing, the brain fills in information

大腦就會自行對記憶空白處

that was not there,

補白，

not originally stored,

原來並未儲存的記憶，

from inference, from speculation,

只是透過推理，猜想，

from sources of information that came to you,

來自於其他源頭的片段，

as the observer, after the observation.

在事後，就當時立場。

But it happens without awareness such that

但這一切都是不知不覺

you don't, aren't even cognizant of it occurring.

你根本就不知道有這回事。

It's called reconstructed memories.

我們稱之為「記憶重建」。

It happens to us in all the aspects of our life, all the time.

我們一輩子，任何事，任何時間，都受記憶重建影響

It was those two considerations, among others --

就是因為記憶重建以及易產生錯誤的目擊者

reconstructed memory, the fact about the eyewitness fallibility --

這兩個理由以及其他因素，

that was part of the instigation

引發了一群上訴律師採取行動

for a group of appeal attorneys

引發了一群上訴律師採取行動

led by an amazing lawyer named Ellen Eggers

由一名很棒的律師愛倫愛格兒(Ellen Eggers)帶領

to pool their experience and their talents together

集合他們的才幹及經驗，向高等上訴法院申請

and petition a superior court

集合他們的才幹及經驗，向高等上訴法院申請

for a retrial for Francisco Carrillo.

重審佛藍西司科．卡瑞羅的案子

They retained me, as a forensic neurophysiologist,

他們聘我為該案的神經醫學專家證人，

because I had expertise

因為我有處理有關目擊者指認和記憶有關問題

in eyewitness memory identification,

的專業知識。

which obviously makes sense for this case, right?

處理這個案子很合理，對吧？

But also because I have expertise and testify about

但也因為我也對人類夜視能力本質很孰悉

the nature of human night vision.

也就此做過法庭專家證人。

Well, what's that got to do with this?

咦，這案子和夜視有關？

Well, when you read through the case materials

對，只要你詳讀有關

in this Carrillo case,

卡瑞羅案的檔案

one of the things that suddenly strikes you is that

有件事該會引起你注意

the investigating officers said the lighting was good

調查員警說

at the crime scene, at the shooting.

凶案發生時，現場光線充足。

All the teenagers testified during the trial

審判時，所有作證的孩子們

that they could see very well.

都說他們當晚能看的清楚。

But this occurred in mid-January,

但這兇殺發生於一月中旬，

in the Northern Hemisphere, at 7 p.m. at night.

這可是北半球，晚上7點。

So when I did the calculations

所以我仔細計算，

for the lunar data and the solar data

當時地球上的案發現場相關的太陽及月球的資料。

at that location on Earth at the time of the incident

當時地球上的案發現場相關的太陽及月球的資料。

of the shooting, all right,

當時地球上的案發現場相關的太陽及月球的資料。

it was well past the end of civil twilight

早就過了民用曙暮光(civil twilight)的時分

and there was no moon up that night.

當晚也沒有月光。

So all the light in this area from the sun and the moon

所以在該區當時所有來自太陽或月亮折射的光線

is what you see on the screen right here.

差不多就像你在銀幕上看到的一樣。

The only lighting in that area had to come

當場所有的光線

from artificial sources,

應該全部來自人工光源，

and that's where I go out and I do the actual reconstruction

所以我回到現場，用感光表，及其他儀器

of the scene with photometers, with various measures

合成不同亮度，以及顏色色溫

of illumination and various other measures of

以重建現場光亮情形

color perception, along with special cameras

使用特殊照相機

and high-speed film, right?

高速底片，記錄這些重建的結果

Take all the measurements and record them, right?

各種數據下，重建現場,然後記錄這些組合.

And then take photographs, and this is what the scene

我照了一堆相片，

looked like at the time of the shooting

這張照片顯示槍擊當時

from the position of the teenagers

從這些少年的位置看起來的樣子

looking at the car going by and shooting.

看著車子，以及開槍的人的方向

This is looking directly across the street

這是直接看到對街的情況

from where they were standing.

從他們所在地看過去。

Remember, the investigating officers' report said

記住，調查員警的報告上說

the lighting was good.

現場光線良好。

The teenagers said they could see very well.

孩子們也說他們可以看的很清楚。

This is looking down to the east,

這張向東邊看過去，

where the shooting vehicle sped off,

犯案車輛逃逸的方向，

and this is the lighting directly behind the father

這是來自被槍擊父親，那些孩子們

and the teenagers.

身後的光線。

As you can see, it is at best poor.

你們可以看到，最多只能說光線昏暗。

No one's going to call this well-lit, good lighting,

沒人會說這是光線充足，明亮，

and in fact, as nice as these pictures are,

而實際上這些照片都很清楚，

and the reason we take them is I knew I was going to have to testify in court,

我拍這些照片是為了要用在法庭上作證時使用，

and a picture is worth more than a thousand words

一張照片比1000個字還有用，

when you're trying to communicate numbers,

當你要傳達一大堆的數字，

abstract concepts like lux, the international measurement

以及抽象概念 - 亮度，國際標準亮度值

of illumination, the Ishihara color perception test values.

衣胥哈拉顏色認知表測試值等。

When you present those to people who are not well-versed

當你對這些非專業的人講這些東西時

in those aspects of science and that, they become

又是科學又是什麼的等等，

salamanders in the noonday sun. It's like

他們就變成正午陽光下的蠑螈。

talking about the tangent of the visual angle, all right?

這好像是討論視角的斜切值，

Their eyes just glaze over, all right?

他們就只會翻白眼。

A good forensic expert also has to be a good educator,

一個好的法庭證據專家也該是個好教育家

a good communicator, and that's part of the reason

好的溝通者，這也是為什麼，

why we take the pictures, to show not only

我們照這些相片，好讓他們

where the light sources are, and what we call the spill,

可以親眼看見當時的光源，以及我們說的漏光，

the distribution, but also so that it's easier

光線分布等，也是為了方便

for the trier of fact to understand the circumstances.

讓那些陪審團的人容易了解狀況。

So these are some of the pictures that, in fact,

這些就是我在審判時，

I used when I testified,

實際使用的照片，

but more importantly were, to me as a scientist,

但更重要的，就一個科學家來說，

are those readings, the photometer readings,

這些測得的數值，感光表讀數，

which I can then convert into actual predictions

我可以把這些數值轉換成實際預測

of the visual capability of the human eye

來反映當時人類眼睛視覺能力

under those circumstances,

在那些狀況下

and from my readings that I recorded at the scene

以及利用當時太陽及月亮資料數值，重建現場的

under the same solar and lunar conditions

重建現場的不同的照片

at the same time, so on and so forth, right,

在同樣時間，同樣的暮光，月光情形等等

I could predict

我可以預測

that there would be no reliable color perception,

當時不可能有可靠的辨色能力，

which is crucial for face recognition,

這對臉孔辨識非常重要，

and that there would be only scotopic vision,

當時只可能有暗視覺，

which means there would be very little resolution,

也就是說在那時對於任何形狀，只有非常低的解析度，

what we call boundary or edge detection,

無法辨別形狀,東西的邊緣

and that furthermore, because the eyes would have been

此外，因為在那種光線下

totally dilated under this light, the depth of field,

瞳孔已經完全放大，人眼的景深，

the distance at which you can focus and see details,

也就是我們能聚焦看清楚的距離，

would have been less than 18 inches away.

只有18英吋不到。(約46公分)

I testified to that to the court,

作證時我說明這些，

and while the judge was very attentive,

法官聽的很仔細，

it had been a very, very long hearing

儘管當時申請重審聽證會已經進行很久，

for this petition for a retrial, and as a result,

結果呢，

I noticed out of the corner of my eye

我注意到，

that I thought that maybe the judge was going to need

可能還得再多拱法官一下

a little more of a nudge

可能還得再多拱法官一下

than just more numbers.

而非引用更多的數據。

And here I became a bit audacious,

我膽子變大了，

and I turned

我轉身對法官說，

and I asked the judge,

我轉身對法官說，

I said, "Your Honor, I think you should go out

「法官大人，我想你該去

and look at the scene yourself."

實地現場勘查。」

Now I may have used a tone which was more like a dare

我大概當時聽起來應該是挑戰法官

than a request — (Laughter) —

而不是請求他 -- (笑聲）--

but nonetheless, it's to this man's credit and his courage

但這個法官真有他的，有膽識

that he said, "Yes, I will."

他說：「好,我會去！」

A shocker in American jurisprudence.

這是美國司法一大震驚。

So in fact, we found the same identical conditions,

所以，我們找了和案發時同樣情形的時候，

we reconstructed the entire thing again,

重建整個現場，

he came out with an entire brigade of sheriff's officers

他在重重警力戒護下來到現場

to protect him in this community, all right? (Laughter)

因為當地治安不好，不是嗎？ （笑聲）

We had him stand actually slightly in the street,

我們讓他站在街上，

so closer to the suspect vehicle, the shooter vehicle,

離嫌犯車輛，槍手坐的車的軌跡近些，

than the actual teenagers were,

比那些孩子們當時站在的地方還要近，

so he stood a few feet from the curb

所以他站在街邊幾尺處

toward the middle of the street.

面向街道。

We had a car that came by,

我們安排一輛車駛過，

same identical car as described by the teenagers, right?

和孩子們的描述的一模一樣的車，

It had a driver and a passenger,

有司機，還有一名乘客，

and after the car had passed the judge by,

車子經過法官身旁後，

the passenger extended his hand,

乘客伸出手來，

pointed it back to the judge as the car continued on,

車子一邊走，他一邊回指法官，

just as the teenagers had described it, right?

就如同孩子們描述的現場狀況，

Now, he didn't use a real gun in his hand,

當然，他手上沒真槍，

so he had a black object in his hand that was similar

他用一個與孩子們形容的槍一樣黑物件。

to the gun that was described.

他用一個與孩子們形容的槍一樣黑物件。

He pointed by, and this is what the judge saw.

車子邊走，槍一邊對著法官，這是法官看到的

This is the car 30 feet away from the judge.

離他30英尺遠。

There's an arm sticking out of the passenger side

一隻手從車前乘客邊伸出

and pointed back at you.

回指向你。

That's 30 feet away.

這是30英尺外。

Some of the teenagers said that in fact the car

有些孩子說槍擊時

was 15 feet away when it shot.

應該是15英尺。

Okay. There's 15 feet.

好，這是15英尺。

At this point, I became a little concerned.

此時，我有些許擔心了。

This judge is someone you'd never want to play poker with.

你絕不想和這法官一起打撲克牌。

He was totally stoic. I couldn't see a twitch of his eyebrow.

他動都不動，眉毛一下也不揚。

I couldn't see the slightest bend of his head.

他的頭連輕微的彎一下都沒有。

I had no sense of how he was reacting to this,

我完全無法判斷他的反應，

and after he looked at this reenactment,

他看完了現場重現後，

he turned to me and he says,

他轉過來問我，

"Is there anything else you want me to look at?"

「還要我看什麼？」

I said, "Your honor," and I don't know whether I was

我說：「法官大人」，也不知道是因為

emboldened by the scientific measurements that I had

這些在我口袋裡精確的科學數據讓我變大膽了，

in my pocket and my knowledge that they are accurate,

這些在我口袋裡精確的科學數據讓我變大膽了，

or whether it was just sheer stupidity,

還是我只是就是蠢

which is what the defense lawyers thought — (Laughter) —

其他辯護律師都認為我蠢 --(笑聲）--

when they heard me say,

當他們聽到我說什麼的時候

"Yes, Your Honor, I want you stand right there

「對，法官大人，我要你站在這兒

and I want the car to go around the block again

我會讓車子再轉回來

and I want it to come and I want it to stop

我會讓車子開過來，然後停下來

right in front of you, three to four feet away,

就停在你面前，3或4英尺外

and I want the passenger to extend his hand

然後我要乘客伸出手

with a black object and point it right at you,

用那個黑色假槍指著你，

and you can look at it as long as you want."

你可以盯著看，看多久都好」

And that's what he saw. (Laughter)

這是他所看到的 （笑聲）

You'll notice, which was also in my test report,

你會注意到，我也在我的報告中指出，

all the dominant lighting is coming from the north side,

所有較亮的光線都來自北邊，

which means that the shooter's face would

也就是說槍手的臉，

have been photo-occluded. It would have been backlit.

在視覺中會光線不足，也就是背光。

Furthermore, the roof of the car

此外，車頂會形成所謂的陰影雲，使得車內更暗。

is causing what we call a shadow cloud inside the car

此外，車頂會形成所謂的陰影雲，使得車內更暗。

which is making it darker.

此外，車頂會形成所謂的陰影雲，使得車內更暗。

And this is three to four feet away.

這是3，4英尺外。

Why did I take the risk?

我為什麼冒險？

I knew that the depth of field was 18 inches or less.

我知道在當時狀態下人眼景深不到18英吋。

Three to four feet, it might as well have been

3 或 4 英尺，和從足球場一端看到另一端沒什麼兩樣。

a football field away.

3 或 4 英尺，和從足球場一端看到另一端沒什麼兩樣。

This is what he saw.

這是他所見到的。

He went back, there was a few more days of evidence

他回去了，證據聽證會又開了幾天

that was heard. At the end of it,

在結束的時候，

he made the judgment that he was going to grant

他批准了

the petition for a retrial.

重審的申請。

And furthermore, he released Mr. Carrillo

此外，他還釋放了卡瑞羅先生，

so that he could aid in the preparation of his own defense

若檢察官決定要重審，也好讓他能回家準備這個案件，

if the prosecution decided to retry him.

若檢察官決定要重審，也好讓他能回家準備這個案件，

Which they decided not to.

結果檢察官決定不重審

He is now a freed man. (Applause)

他被釋放了（掌聲）

(Applause)

(掌聲）

This is him embracing his grandmother-in-law.

這張照片裡，他擁抱他太太的祖母。

He -- His girlfriend was pregnant when he went to trial,

他的女友在他受審時已懷孕，

right? And she had a little baby boy.

生下了小男生。

He and his son are both attending Cal State, Long Beach

他和他兒子現在都就讀於加州大學(Cal State)長灘(Long Beach)校區

right now taking classes. (Applause)

兩個現在都在上課（掌聲）。

And what does this example --

這個例子 -

what's important to keep in mind for ourselves?

教我們什麼寶貴的教訓？

First of all, there's a long history of antipathy

首先，長久以來在美國的司法環境

between science and the law

科學與法律一直不相容。

in American jurisprudence.

科學與法律一直不相容。

I could regale you with horror stories of ignorance

我可以告訴你很多很多出於無知的恐怖故事，

over decades of experience as a forensic expert

全都來自於我幾十年來從事法庭專家證人

of just trying to get science into the courtroom.

嘗試把科學帶進法庭的經驗。

The opposing council always fight it and oppose it.

對方律師總是反對，百般阻撓。

One suggestion is that all of us become much more

有個建議，就是我們全都應該

attuned to the necessity, through policy,

接受更多的科學進入法律領域

through procedures,

這是必要的，透過政策，

to get more science in the courtroom,

透過恰當程序，

and I think one large step toward that

完成做這件事的一大步。

is more requirements,

就是增加要求

with all due respect to the law schools,

讓法學院把科學，

of science, technology, engineering, mathematics

科技，工程，數學納入必修課程

for anyone going into the law,

要求每個法律學生修習

because they become the judges.

因為這些學生將來會成為法官。

Think about how we select our judges in this country.

想想在美國我們如何選擇法官？

It's very different than most other cultures. All right?

和其他多數文化大不相同，不是嗎？

The other one that I want to suggest,

另一件我建議的事：

the caution that all of us have to have,

我們全部都得小心

I constantly have to remind myself,

我一直提醒自己

about just how accurate are the memories

記憶並不精確，

that we know are true, that we believe in?

不管是那些我們認為是真的，或是我們信任的記憶。

There is decades of research,

幾十年來的研究，

examples and examples of cases like this,

無數與此相似的案例，

where individuals

正都是人們都是這麼信任自己的記憶。

really, really believe. None of those teenagers

這些孩子們。

who identified him

指認兇嫌時

thought that they were picking the wrong person.

沒人會認為自己會認錯人。

None of them thought they couldn't see the person's face.

沒有一個認為自己會看不清楚那個人的臉

We all have to be very careful.

我們都得非常小心

All our memories are reconstructed memories.

我們所有的記憶都經過重建

They are the product of what we originally experienced

它們來自我們的原始經驗

and everything that's happened afterwards.

以及事後所有的經驗。

They're dynamic.

這些記憶是動態的。

They're malleable. They're volatile,

可以不斷修改，不穩定，

and as a result, we all need to remember to be cautious,

結果呢，我們都要記得對於我們的經驗精確度

that the accuracy of our memories

要謹慎小心，

is not measured in how vivid they are

不在於我們記得多清晰

nor how certain you are that they're correct.

也不在我們多確定它們有多正確。

Thank you. (Applause)

謝謝。 （掌聲）