(delivering the judgment of the court): The accused, Ang Soon Huat, was charged as follows:

You, Ang Soon Huat, on or about the 29th day of September 1986 between 10.50pm and 11.15pm, in Singapore, did traffic in a controlled drug specified in Class 'A' of the First Schedule to the Misuse of Drugs Act (Cap 185), to wit, by transporting one plastic packet of drug containing not less than 18.77g of diamorphine in motor car JBJ 3072 from Immigration Woodlands Checkpoint to the carpark at Woodlands Cinema without any authorization under the said Act or the regulations made thereunder and you have thereby committed an offence under section 5(a) and punishable under section 33 of the Misuse of Drugs Act.

Case for prosecution

The evidence adduced by the prosecution proves beyond any doubt that the accused did traffic in a quantity of diamorphine on the day and time in question. The accused was arrested near his car and a plastic packet was found in the glove compartment thereof as a result of a trap laid for him by the officers of the Central Narcotics Bureau. The entrapment was made possible when the accused tried to reach one Lim Lye Huat through Lim's pager when Lim was in the custody of the CNB officers after his arrest for trafficking, possession and consumption of a similar drug. Lim was instructed by a CNB officer to arrange for the officer to buy about a ¼ pound of heroin from the accused. The arrangement was successfully made and it led to the arrest of the accused with a plastic bag containing a pinkish granular substance.

The evidence adduced by the prosecution to prove that the weight of the diamorphine in the plastic packet was not less than 18.77g is as follows. After the accused was arrested, he and his wife (who was with him in the car at the time of the arrest) were taken to CNB headquarters. The plastic packet and all the other things that were seized from the accused and his wife were also brought to CNB headquarters. The packet was weighed on 30 September 1986 and found to weigh 111.4g.

According to NO Lee Kiong Lock, he sent the plastic packet to the Department of Scientific Services ('DSS') on 30 September 1986 at about 11.40am for analysis and report. DSS received the packet and an analysis was done. For convenience, we shall hereafter use the expression 'the exhibit' to refer to the contents of this plastic packet.

The accused has not challenged this part of the prosecution's case. What he has challenged was the weight of the diamorphine in the exhibit. It is therefore necessary to review the prosecution evidence on how the weight of 18.77g was arrived at by Dr Chow.

(1) Testimony of Loh Chung Sin (PW7): Loh was a senior laboratory technician (since 1980) in the DSS with about 16 years' of work experience. On or about 1 October 1986, he received from Dr Chow the plastic packet. He then weighed the packet on a semi-micro balance (ie a balance that is accurate to four decimal points) which, in accordance with laboratory procedure, he had checked for accuracy prior to the weighing. He found that the weight was 111.4529g. He then slit open the packet and emptied the contents into a blender which was kept clean and dry for that purpose. He then weighed the empty plastic packet and found it to be 1g exactly, thus giving a net weight of 110.4529g for the granular substance.

Loh then started the blender and allowed it to operate for five minutes. He then repeated the process twice. He said that after the first operation, the substance was about 95% pulverized and that after the third operation, the substance was completely pulverized into a fine powder. (We have inspected the exhibit tendered in court and agree that it is a fine powder but it was then in a hardened form.) After the blending, he then put the powdered exhibit into a pre-weighed plastic bag. He then took a small amount of the powder and put it into three crucibles for the purpose of testing the presence of heroin by means of three kinds