Question

If DNA from an evidence sample and DNA from a suspect or victim share a profile that has a low frequency in the population, this suggests that the two DNA samples came from the same person; the lower the frequency, the stronger the evidence. But the possibility remains that the match is only apparent—that an error has occurred and the true profile of one of the sources differs from that reported by the laboratory. Please discuss the ways that laboratory errors, particularly errors that might falsely incriminate a suspect, can arise, how their occurrence might be minimized, and how to take into account the fact that the error rate can never be reduced to zero.

Please discuss the quality assurance and control.

Answer 1

The maintenance of high laboratory standards rests on a foundation of sound quality control and quality assurance.

Quality control and quality assurance refer to related but distinct components of a laboratory's effort to deliver a quality product.

Quality control refers to measures that are taken to ensure that the product, in this case a DNA-typing result and its interpretation, meets a specified standard of quality.

Quality assurance refers to measures that are taken by a laboratory to monitor, verify, and document its performance.

Regular proficiency testing and regular auditing of laboratory operations are both essential components of Quality assurance programs.

Quality assurance thus serves as a functional check on Quality cantrol in a laboratory.

Demonstration that a laboratory is meeting its Quality cantrol objectives provides confidence in the quality cantrol of its product.

Individual analysts have education, training, and experience commensurate with the analysis performed and testimony provided.

Analysts have a thorough understanding of the principles, use, and limitations of methods and procedures applied to the tests performed.

Analysts successfully complete periodic proficiency tests and their equipment and procedures meet specified criteria.

Reagents and equipment are properly maintained and monitored.

Procedures used are generally accepted in the field and supported by published, reviewed data that were gathered and recorded in a scientific manner.

Appropriate controls are specified in procedures and are used.

New technical procedures are thoroughly tested to demonstrate their efficacy and reliability for examining evidence material before being implemented in casework.

Clearly written and well-understood procedures exist for handling and preserving the integrity of evidence, for laboratory safety, and for laboratory security.

Each laboratory participates in a program of external proficiency testing that periodically measures the capability of its analysts and the reliability of its analytic results.

Case records - such as notes, worksheets, autoradiographs, and population data banks - and other data or records that support examiners' conclusions are prepared, retained by the laboratory, and made available for inspection on court order after review of the reasonableness of a request.