Findings from re-tests showed that the use of a higher-than-normal concentration of a chemical had not affected most of the DNA test results for 87 criminal cases, said the Health Sciences Authority (HSA) yesterday.
In January, HSA said it was re-testing about 2,000 DNA samples in the 87 cases.
This was done after it discovered that human error had resulted in a chemical of unusually high concentration being used for the DNA testing process in HSA's DNA Profiling Laboratory from October 2010 to August last year.
As a result, this caused the DNA test, which can be used to help identify people present at a crime scene, to be less sensitive. This meant that some of the DNA samples could not be presented in court as evidence.
Using the chemical at the right concentration in a test could mean that additional samples could be detected and presented as evidence in court. HSA estimated in January that these additional samples could amount to fewer than 5 per cent of all the samples.
The authority said yesterday that, after completing the re-testing, an additional 2.9 per cent of the samples were detected and can be used in court as evidence.
This places seven additional people at the crime scenes in several of the affected criminal cases.
All the DNA re-test reports have been submitted to police and the Central Narcotics Bureau.
The Attorney- General's Chambers (AGC) will assess all available evidence, including the re-test results, in arriving at the appropriate legal decision in each case.
The laboratory manager who made the error in preparing the chemical at a higher concentration has since been issued a warning letter.
HSA said a review committee set up to look into the incident recommended that no further action be taken against the manager. This is considering "the commendable action by (him in reporting) the error promptly", the authority added.
The committee also observed that the number of samples received for testing by HSA's DNA Profiling Laboratory has increased in the last few years.
Noting that there was no corresponding increase in manpower, the committee said that this presented a "potential stress on the laboratory".
The committee also recommended that staffing for the laboratory be reviewed, taking into account its current and anticipated workload.
HSA said that it has taken action to improve processes in the laboratory and introduced tighter procedural checks on the chemical-preparation process.
The laboratory now purchases commercially prepared chemicals, where available. Any chemical preparation is done with additional supervision.
In a separate statement on the DNA tests, AGC assured that each criminal case "will be reviewed thoroughly to ensure that justice is done and that no accused person is prejudiced".
Of the 87 criminal cases that needed re-testing, 25 have been reviewed by the AGC thus far, and the re-test results did not lead to any change in the legal decisions made.
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