But we’ve achieved a partial victory: they are now describing the statistics properly.
Remember the original passage that so distressed me:
Jurors were not told, however, the statistic that leading scientists consider the most significant: the probability that the database search had hit upon an innocent person.
In Puckett’s case, it was 1 in 3.
As I said in this post:
I believe the article meant to say this: if the database had consisted only of innocent people, there was a 1 in 3 chance that the search would hit on an innocent person. Phrased that way, the statement would be accurate, and would shed light on the question of how surprised we should be by a database hit.
But that’s not what the paper said. Instead, the article indicated the odds that the search “had hit” on an innocent person — in other words, the odds that Puckett himself was innocent.
The italics are in the original.
Note that I emphasized two problems with the passage:
1) The article said “had hit” when it should have said “would hit.”
The actual search resulted in only one hit: to the defendant. The article said there was a 1 in 3 chance that the search “had hit” on an innocent person. That was the same as saying there was a 1 in 3 chance that the defendant was innocent — which is wrong.
2) The article omitted a key assumption: that the database consisted entirely of innocent people.
By leaving out this assumption, the article further created the impression that the odds referred to the odds that the particular defendant on trial was innocent.
Yesterday, the L.A. Times reported on a related California Supreme Court decision that refused to require the database adjustment touted by the original L.A. Times article. This time around, reporters Maura Dolan and Jason Felch do a much better job explaining the 1 in 3 statistic:
The Times reported in May that a San Francisco judge presiding over a murder trial allowed jurors to hear the rarity statistic of 1 in 1.1 million. But the judge refused to permit the defense to reveal that there would be a 1 in 3 chance of finding a DNA match in the database, even if the actual perpetrator was not among the profiles.
The two errors I complained about before are now gone.
Proper use of forward-looking “would be” verb tense? Check.
Inclusion of key assumption that the perpetrator was not in the database? Check.
No, the paper never issued a correction. But I’m going to count this as a victory.
Not for me. For accuracy.