4.5 Two case studies 157
talk to the driver. They are both normal,
unsurprising events in a typical office day, and
there is no obvious reason to believe one rather
than the other. It is only because they conflict
that we would question them at all. But since
they do conflict, we have to question them.
Corroboration
Where Depp’s statement scores over Rita’s is
that it gets some measure of corroboration
both from the driver and from the manager
herself. Rita has no witnesses or circumstances
to corroborate her counter-claim. However,
the corroborating evidence is not 100% solid.
The manager says that she is ‘fairly certain’ the
deputy manager’s door was open and his office
was empty when she left. The driver, too, gives
rather vague estimates: ‘I was with Mr Depp...
around 10.00. We talked for quite a long time.’
Conceivably, by this reckoning, the meeting
could have ended in time for Depp to go back
to his offices before Mrs Mann returned. So,
although the corroboration of two other
witnesses adds to Depp’s credibility, it does not
by any means remove all doubt about his
version of events.Suppositional reasoning: ‘What if... ?’
So far it looks very much like a case of one
person’s word against another’s. But there is a
way forward. It involves a very useful
technique known as suppositional reasoning.
Suppositional reasoning typically starts with
phrases such as ‘Supposing.. .’ or ‘What if... ?’
For example, suppose that the secretary is
right: that Depp did go into the manager’s
office while she was away, which was also
during the period when the money went
missing. What would follow from this? It
would mean, of course, that Depp had an
opportunity to take the money. It would also
mean that he was lying when he said he was
away from the offices throughout the
manager’s absence, unless he had mysteriously
forgotten where he had been that morning.
And it is hard to understand why he would lie
unless he had something to hide. But would
he really have walked into the manager’sCommentary
What we have here are two conflicting stories.
The secretary, Rita, claims that the deputy
manager went into the manager’s office twice,
once while the manager was in there and once
after she had left. The deputy manager, Mr
Depp, confirms that he went into her office
the first time, but denies the second. He claims
that during the time he was alleged to have
entered the manager’s office he was in the
canteen talking to a driver. At some time
during all this, some money went missing
from the safe. The secretary’s statement, if
true, casts considerable suspicion on Depp.
We will start by considering the witnesses
themselves. The three occupants of the
Management Suite are the manager, the
deputy manager and the secretary. The driver
is also a witness. Their ranking in the company
is probably in that order. So does this mean we
should rank the reliability of their evidence in
the same way: the manager’s more than the
deputy’s, the deputy’s more than the
secretary’s, the driver’s least of all?
In a word, no. In some cases there may be
more reason to trust a manager’s judgement
over a junior employee’s, on the grounds of
their respective qualifications and experience.
But we are not talking about judgement here,
only about honesty and accuracy. You may
argue that a manager has more to lose than a
secretary. But it would be quite unjustified to
assume that therefore the secretary is more
likely to be dishonest. It would be even more
unjustified to assume that the secretary was
less likely to be accurate in her statement. If
you looked carefully at the evidence you will
have seen that it is the secretary who is the
most exact in the information she gives, the
manager the most vague and imprecise. And it
should not be overlooked that the manager left
the safe unlocked, suggesting some absent-
mindedness or carelessness on her part.
What about the statements themselves: are
they equally plausible? On the face of it, yes.
There is nothing improbable about Depp going
into the manager’s office, or about his going to