“Say there’s a robbery,” she said, “and there’s a getaway
car and a bunch of robbers with guns. Witness One may then recall three robbers, two with masks and one with a hat, and a black car.”
She set down one black pen cap and two paper clips.
“Witness Two may remember four robbers, all with masks, and a blue car.” She added two paper clips and replaced the black cap with a blue one. “And maybe they thought they saw a motorcycle.”
She pushed a roll of tape past.
“Witness Three is sure it was three robbers,” she went on, taking away a paper clip. “One wore a mask and a hat, and the car was green. I don’t have a green cap, so . . . anyway. Witness Three is sure of what he saw. That’s a big deal—people who think they have good memories are sometimes the least reliable but the most likely to sway others. And that witness then says that the motorcycle was with the green car.”
“Is that the tape?” David asked. “And the green car is that blue cap?”
“The point is,” Stevie said, “now that Witness One has talked to Witness Three, and Witness Three seems really sure about what they saw, Witness One may now think back and see three robbers in hats, not masks. Witness Two now questions the masks and thinks the car was green. And one robber was very tall. Witness Three claims they were all tall. And suddenly everyone starts to say that they were all tall, and that the motorcycle was with the green car.”