USA: "Panel debunks method used to link bullets to suspects "

[cuchulainn]

from the Los Angeles Times (although it appears on the San Francisco Chronicle's webpage)

http://www.sfgate.com/cgi-bin/article.cgi?f=/chronicle/archive/2003/11/21/MNG4S380661.DTL

Friday, November 21, 2003

Panel debunks method used to link bullets to suspects

Charles Piller, Los Angeles Times

A panel of government scientific advisers has found that an FBI forensic technique long used to link bullets with assailants is scientifically flawed and potentially misleading to juries -- a finding that could affect hundreds of past convictions.

The method, which measures the likelihood of a chemical match between bullets found at crime scenes and in those found in the possession of a defendant, has been used for more than three decades. The Los Angeles Times obtained a draft summary of the report, which is expected to be formally released by the National Research Council in early December.

"In the future, it would be very difficult for prosecutors to get that kind of evidence admitted," said William Thompson, a professor of law and criminology at UC Irvine. "It raises substantial concerns about the viability of convictions obtained based on such statements in past cases."

The FBI had no comment.

The National Research Council also would not comment on the report, but a source close to the study indicated that its primary conclusions would stand in the final version.

The report is "a very substantial development -- a significant indictment of the technology," said David Faigman, a professor of law at UC's Hastings College of the Law. "The NRC has such prestige that I can't imagine that a court, after the NRC report, would permit this kind of testimony."

The chemical analysis of bullets found at crime scenes involves analyzing the material for traces of contaminants or additives, such as tin and antimony.

The precise amount of contaminants is then compared to the results from bullets found in a suspect's possession.

FBI examiners have often stated or implied in court that a bullet can be traced to a specific manufacturing batch -- even to a particular box.

The technique has offered a way to solve murders and other crimes involving gun violence when no gun was found. It has strengthened weak cases in which evidence is scarce or circumstantial.

A Times investigation of the technique published in February suggested that the FBI's use of lead-analysis evidence might have been based on faulty assumptions that greatly overstated its scientific significance.

After criticism from independent experts, the FBI commissioned the lead- analysis study from the National Research Council, considered the United States' pre-eminent group for assessing science and technology. The panel, which included experts in chemistry, law and statistics, studied the method for nearly 10 months.

The panel substantially agreed with recent research indicating that bullets from the same source of lead can significantly vary in their chemical makeup, and bullets from different sources -- even those manufactured years apart -- can share nearly identical amounts of trace elements.

The finding contradicted some prosecutors' depictions of each batch of lead as being unique, like a snowflake or fingerprint. The study suggests that the number of "matching" bullets was impossible to determine and could be in the tens of millions or far higher -- dramatically reducing the significance of a match.

Although the panel stopped short of condemning the technique outright, it sharply disagreed with how FBI examiners have often represented bullet evidence in court.

 

[gun-fucious]

AP: FBI Bullet Analyses Flawed, Imprecise

http://story.news.yahoo.com/news?tm...ap/20031121/ap_on_go_ca_st_pe/fbi_lab_bullets

AP: FBI Bullet Analyses Flawed, Imprecise


By JOHN SOLOMON, Associated Press Writer

WASHINGTON - In a finding that could affect thousands of criminal cases, the National Academy of Sciences (news - web sites) has concluded that some techniques the FBI (news - web sites) has used for decades to match bullets to crimes are flawed or imprecise.

The study, expected to be released in the next few weeks, makes about a half-dozen recommendations to improve the FBI lab's science used to match bullets through their lead content.


The academy's findings, which are in final draft form, were described to The Associated Press by several people involved in the study. They would speak only on condition of anonymity.


The study specifically urges the bureau's chemists to stop a practice known as data chaining that chemists have used in the past to match bullets to a crime.


In data chaining, scientists can conclude that if the lead content of bullet A matches bullet B, and bullet B's content matches bullet C, then it is safe to testify that bullet A and bullet C are a match even if their test results don't match identically. Said another way, the FBI can match two dissimilar bullets if they can find a third — from a manufacturer, for instance — that matches both.


The FBI science relies on the theory that bullets from the same batch of lead share a common chemical fingerprint.


Charles Peters, an FBI's expert witness in cases involving bullet lead comparison, testified recently that data chaining — the technique disavowed by the academy — was important to matching bullets.


"I'm a fan of chaining," Peters testified in April in a case in Alaska. "If we had great precision, really good precision ... and we didn't do something like chaining, or something like that, nothing would ever match."


A reference in the latest draft of the academy report indicates the FBI may abandon the data-chaining technique, the sources said. FBI officials said Thursday night they had not seen the report and could not comment on it.


"I cannot comment on a draft report that is still being peer reviewed and subject to change," National Academy of Sciences spokesman Bill Kearney said Thursday.


Citing specific examples of conflicting or inconsistent testimony by FBI experts, the study also recommends that lab analysts' work and testimony be reviewed by a peer to ensure accuracy and precision, the sources said.


The FBI lab's director has been trying to increase the number of peer reviews inside the lab.


The academy's recommendations are likely to have a huge impact, opening the door for appeals from defendants convicted in past cases where bullets were matched by the FBI using lead analysis. It also could force FBI lab witnesses to more narrowly describe the statistical significance of their findings in future cases.


The FBI has been the prime practitioner of lead bullet comparisons in the United States, and has used it for decades, dating to around the time of President Kennedy's assassination 40 years ago. A database of lead test results kept by the agency had more than 13,000 samples in the late 1990s, FBI officials have told the AP.


The FBI most commonly identifies bullets recovered from a crime by firing new bullets from the suspect's weapon and comparing the markings left by the gun barrel on the test bullet with the crime scene bullet. But that method only works when the crime scene bullet is in good shape or if police have the suspect weapon.


In cases where recovered crime scene bullets are fragmented or disfigured or a suspect's weapon is unavailable, the FBI has turned to chemical analysis to try to determine whether the bullet's lead content is comparable to the same manufacturer, lead source or box of bullets connected to the suspect.


When the lab makes a match, its experts testify that two bullets are "analytically indistinguishable."

_


FBI Lab Director Dwight Adams earlier this year asked the academy to review the lead bullet identification process after one of the bureau's most respected metallurgists, after he retired, began openly challenging his former employer's science. The FBI paid for the study by the academy, which is one of the nation's premiere scientific institutions.

The former FBI metallurgist, William Tobin, and his colleagues have published research stating that bullets from the same lead source had different chemical makeups and bullets from different lead sources appeared chemically similar, challenging the very premise of the FBI's science.

Testifying as a defense expert, Tobin has cited evidence that FBI lab experts have testified in conflicting manners about how lead composition can identify bullets and link them to criminals.

Iowa State University has conducted research that drew similar conclusions.

"The fact that two bullets have similar chemical composition may not necessarily mean that both have the same origin. ... The leap from a match to equal origin is enormous and not justified given the available information about bullet lead evidence," Iowa State researchers reported.

 

[SDC]

I can't imagine anyone being so stupid as to base a CONVICTION on this sort of evidence alone, because how many bullets are manufactured out of a given lot or batch of lead; thousands, maybe millions?

 

[TheBluesMan]

Duplicate threads merged.

 

[Brett Bellmore]

This "data chaining" business is so stupid I have trouble believing even a government employee could think it was legitimate. The institutions that trained their scientists would be fully justified in breaking into their homes to confiscate their diplomas.

 

[Standing Wolf]

Well, yeah, but the F., the B., and the I. caught Patty Hearst, didn't they?

 

[Coronach]

I'm not familiar with the procedure, but the theory of data-chaining is fine, as long as it is related to juries as being what it is...you're basically saying that a bullet recovered from the scene matches the chemical composition of bullets owned by the defendant. As such, thats a nice piece of the puzzle, another brick in a circumstantial case, but (forgive the pun), it ain't no smoking gun.

The academy's recommendations are likely to have a huge impact, opening the door for appeals from defendants convicted in past cases where bullets were matched by the FBI using lead analysis. It also could force FBI lab witnesses to more narrowly describe the statistical significance of their findings in future cases.

This would seem to be the correct course of action: making sure that the processes is described properly to the jury. When Joe Juror hears

"analytically indistinguishable."

that sounds an awful lot like a fingerprint-level match, which this...very much is not.

Don't despair too much, however, I'm sure defense attorneys go to great lengths to point this out.

Mike

 

[Brett Bellmore]

Well, in THAT spirit, rolling dice is fine, so long as you explain to the jury that you pulled the result out of your rear end.

The whole idea of matching alloys in the first place is only valid once you've done extensive, and I mean REALLY extensive, hundreds of thousands of bullets from different manufacturers, different processes, different points in the pour. And if you've done that research, data chaining just throws the results of it away, depending on the sheer luck of the draw. It's junk science.

And given the behavior of federal law enforcement, unless they can show that they actually DID do that extensive research, and did it properly, we should conclude that it's ALL junk science.