RENEE MONTAGNE, host:
The word circumstantial has been all over news reports on the anthrax investigation, as in the evidence that Bruce Ivins was the anthrax killer is largely circumstantial. As we just heard from his attorney, Paul Kemp, the government has no confession or other direct evidence tying Ivins to the attacks. NPR's Ari Shapiro, though, has this report on the role circumstantial evidence plays in the legal system.
ARI SHAPIRO: A crowd of eyewitnesses or a bloody murder weapon can be a prosecutor's dream come true.
Professor MARY CHEH (George Washington University): But you have to deal with real life.
SHAPIRO: And in real life, says George Washington Law Professor Mary Cheh, circumstantial evidence may be the best a prosecutor has.
Prof. CHEH: Circumstantial evidence is just evidence of an indirect nature.
SHAPIRO: It allows you to infer conclusions from the available facts. For example, imagine a man and a woman check into a hotel. They come out the next morning. They do that repeatedly.
Prof. CHEH: Maybe I don't have direct evidence that, you know, they're having an affair, but I infer rather strongly from those facts. Now, maybe they're meeting on successive occasions to plan the church picnic.
SHAPIRO: If this were an adultery trial, a defense lawyer might make that argument, and the jury would have to decide whether it was credible. The law says this is a legitimate way to prove a crime.
Prof. CHEH: You are allowed in law, for example, to prove a murder and you don't even have a body. So you have to infer that there's been a death and that it's been murder.
SHAPIRO: And prosecutors have won cases that way. The former U.S. attorney in Baltimore, Tom DiBiagio, says it happens all the time.
Mr. THOMAS DIBIAGIO (Former U.S. Attorney): You're describing probably 90 percent of the cases that are tried every day.
SHAPIRO: For example, when someone robs a bank wearing a ski mask, no one may be able to definitively identify the robber. But imagine the FBI searches the suspect's house.
Mr. DIBIAGIO: And you uncover a ski mask and some cash. Well, you know, everybody could have a ski mask, it's just these are pieces of evidence that link him to the crime.
SHAPIRO: Some circumstantial evidence can be incredibly damning; other evidence less so. A jury weighs it all and reaches a conclusion. And that's one reason the anthrax mystery is so unsatisfying. Bruce Ivins committed suicide and the government moved to close the case so a jury will never decide whether the government had enough evidence for a conviction or not.
Donald Stern used to be the U.S. attorney in Boston.
Mr. DONALD STERN (Former U.S. Attorney): The jury here is, I suppose, the public at-large, which can draw its own conclusions based upon the evidence the government has presented and the arguments and contrary positions that his defense lawyer has taken.
SHAPIRO: To make things even more ambiguous, the FBI had not completely finished its investigation when Bruce Ivins committed suicide. Just yesterday a judge approved search warrants for two public library computers that FBI agents watched Ivins use days before he killed himself. An agent said the computers could contain suicide letters, photographs or other information relevant to the investigation.
When Washington D.C.'s U.S. Attorney Jeff Taylor spoke at a press conference this week, he made it sound like the FBI had all the evidence it needed.
Mr. JEFFREY TAYLOR (U.S. Attorney): Based upon the totality of the evidence we had gathered against him, we are confident that Dr. Ivins was the only person responsible for these attacks.
SHAPIRO: That may be so but the government would like to be even more confident. The night Ivins died, agents were planning to meet with his lawyer. They were going to urge Ivins to confess. If he'd done that, all of the circumstantial evidence would have been irrelevant, but Ivins did not confess. He maintained his innocence and he overdosed on painkillers, prematurely ending this investigation seven years after it began.
Ari Shapiro, NPR News, Washington.
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