of his evidence, why he cannot give such an explanation. Still, John’s position
will be strengthened if he can also show by cross examination or evidence
some explanation for how Bill died -
that someone else had motive and
opportunity to murder Bill, that Bill died accidentally or that Bill died by his
own act.
Dependent and Independent Facts
In principle facts of a case can be either dependent or independent. Where
parties use a persuasive theory, which they commonly do, facts are presented
as dependent.
The significance of this is that, generally speaking, the probability of the
contested facts in the persuasive theory tends to rise and fall together. This is
especially likely when each side presents a persuasive theory, as is commonly
the situation. Under the complementarity rule, as the case of one party rises,
the case of the other party falls correspondingly.
Inherent Implausibility
On basis for disbelieving evidence is that it portrays a fact that is inherently
improbable. Some facts are inherently implausible because they rarely occur.
For example, a person walking along the footpath sees a bundle of bank notes
on the ground and does not pick them up.
Combinational Implausibility
Love and marriage, love and marriage
/ Go together like a horse and
carriage
Dad was told by mother / You can’t have one without the other
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Evidence of X and Y is more plausible if X and Y naturally go together;
conversely the evidence is less plausible if X and Y are unlikely to occur
together. In other words, an event that is not inherently implausible can still be
improbable when it occurs in conjunction with one or more other events. In
this case the two (or more) events separately may be probable enough, but it is
improbable that they happened together or in the sequence alleged. Sometimes
this form of improbability is referred to as a lack of internal consistency.
Internal consistency is illustrated by the maxim “where there is smoke there is
fire”. Evidence is not credible if it tells of a fire without smoke
610
or smoke
without a fire. Conversely, it is credible if it tells of both smoke and fire.
609
Frank Sinatra Love and Marriage
610
In saying this we are adding to the maxim. In original form it is that there is
no smoke without fire. We are now stating the converse, that there is no fire
without smoke. This does not logically follow, but in a practical sense, and this is
the sense that most matters, is largely true.
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