The case of the fingerprint in the switch room

Copper lightning rods were stolen from the switch rooms of a Kowloon housing estate on a day in December 2010. The burglar appeared to have had a key because there was no damage to the doors, which locked automatically. No one saw the burglary, so there was no visual identification evidence. The only evidence against the defendant, Mr Chiu, was that his fingerprint was found on the inside of the wooden door of one of the switch rooms. The expert witness could not tell how long the fingerprint had been there.

If you were the judge, would you convict Mr Chiu of burglary? Perhaps before you decide, you need to know more about the switch rooms, because it matters a great deal whether the fingerprint was found, say, on the door of a public washroom or on the door of one's bedroom.

There were 13 switch rooms, all of which could be opened by a single key. Two keys were kept at the ground floor counter. Other keys were kept at a nearby control room. The keys could be signed out by workers - which happened "very often" - and when signed out a record was made in a register book. No one had signed out a key "from the counter" on the day in question.

However the register book was never produced in evidence, leaving it unknown if the defendant's name ever appeared in the book.

One might wonder next what the defendant had to say about his fingerprint. Mr Chiu chose to remain silent, as was his constitutional right, thereby putting the onus on the prosecution to prove his guilt.

In these cases, the judge will normally ask if the defendant's guilt is the only reasonable inference to be drawn from the evidence.