ISSUED BY: Forensic QA Manager PUBLISHED DATE: 09/24/2019
7.2.1 Selection and Verification of Methods 7.2.1.1
The Crime Laboratory (CL) has documented procedures for each discipline/subdiscipline that performs testing. The procedures are contained in each discipline's Unit Methods Manual (UMM) and/or Training Manual. Procedures shall be written in a manner that provides consistent and acceptable testing results, regardless of the individual performing the test or the time in which the test is performed. The procedures in these manuals define the methods of analysis; necessary method controls; use, maintenance and/or calibration of all relevant equipment and instrumentation; handling, transportation, storage, and preparation of items for testing; the use of reference material, where appropriate; and provide instructions on how to perform the testing. Where appropriate, the manuals address an estimation of measurement uncertainty and/or statistical techniques used for the analysis of test data and sampling. If available, current manufacturer's instructions on the use of equipment and instruments shall be maintained in each unit. All instructions, standards, manuals, and reference data relevant to the work of the CL shall be kept up to date and made available to CL personnel. Where practical, these items may be placed in the PBSO Portal or Qualtrax document control center. NOTE: If manufacturer’s instructions are used in lieu of a written procedure, they shall be maintained as a controlled document in the Qualtrax document control center.
7.2.1.1.1 Unknown/Known Comparisons
All test methods that involve the comparison of an unknown to a known shall require the evaluation of the unknown item prior to comparison to one or more known items, to identify characteristics suitable for comparison, and if applicable, characteristics suitable for statistical rarity calculations. Characteristics include, but are not limited to, alleles in a DNA profile, friction ridge detail in a latent print, or criteria for evaluation of mass spectrometry fragments and ratios in a seized drug sample or a toxicology sample extract.
7.2.1.2 Method Documentation
The most current Unit Methods Manual for each discipline is authorized, controlled, maintained, and readily available to the CL staff in the Qualtrax document control center. The authorization process helps to ensure that adopted procedures meet acceptable scientific standards. When alternative procedures are available, individual analysts can exercise discretion in selecting the analytical method most appropriate to the evidence examined.
Appropriate controls and standards shall be specified in the methods used by each discipline and their use documented in the case record.
7.2.1.3 Selection of Methods
The CL shall use test methods including methods for sampling which meet the needs of the customer and which are appropriate for the tests performed, preferably, methods published
in international, regional, or national standards. The CL shall ensure it uses the latest valid edition of a standard unless it is not appropriate or possible to do so. When necessary, the standard shall be supplemented with additional specific descriptions to ensure consistent application. Non-standard analytical methods and laboratory developed analytical methods are used only if properly validated to address the specific use of the method.
Changes to an authorized procedure shall be made in accordance with the requirements of the Quality Assurance Manual (QAM).
7.2.1.4
Normally, requests for service by a customer are for a category of analysis and not a specific method. In this case, the CL will select the approved tests that are appropriate to meet the service request of the customer.
The customer may request the type of tests used in the testing process at any time. However, if the customer requests any service or test that is outside the capabilities of the CL, or a method of analysis that is inappropriate or out of date, the Unit Manager or designee shall inform the customer.
7.2.1.5 New Methods
The CL shall verify that it can properly perform methods before using them on casework by ensuring that it can achieve the required performance. Prior to implementation of a validated method new to the CL, the reliability and reproducibility of the procedure shall be documented in-house against any documented performance characteristics of that procedure. Each Unit shall maintain records of the performance verifications in perpetuity.
7.2.1.6 Developed Methods
The Unit Manager and/or Technical Leader shall authorize the content and design prior to the start of the method development. The development of analytical methods are a planned activity carried out by a qualified analyst equipped with adequate resources. The Unit Manager or Technical Leader shall authorize any changes to the original design during the course of the method development study.
7.2.1.7 Method Deviation
Deviation from procedures shall only occur if technically justified, validated, authorized, and documented in the case record, and where appropriate, accepted by the customer.
Due to the widely variable nature of evidence, some examinations cannot be performed exactly as written in the UMM. Unexpected deviations from written technical procedures may occur with unusual evidence and shall be recorded on examination documentation. The Unit Manager or Technical Leader shall document authorization for minor deviations in the case record.
ISSUED BY: Forensic QA Manager PUBLISHED DATE: 09/24/2019 Laboratory Director (CLD) that shall be documented in the case record.
7.2.2 Validation of Methods
7.2.2.1 Validation of Non-Standard or Lab-Developed Methods
The CL shall validate non-standard methods, laboratory-developed methods, and standard methods used outside their intended scope, or otherwise modified. The validation shall be as extensive as is necessary to meet the needs of the given application.
The discipline performing the validation shall record the results obtained, the procedure used for the validation, and a statement as to whether the method is fit for the intended use. The results shall be formatted in a way that allows for verification against design requirements.
Techniques used for the determination of performance of a method may include, but is not limited to, one or more of the following:
a. Calibration or evaluation of bias and precision using reference standards or reference materials;
b. Systematic assessment of the factors influencing the result;
c. Testing method robustness through variation of controlled parameters, such as incubator temperature, or volume dispensed;
d. Comparison of results achieved with other validated methods; e. Interlaboratory comparisons;
f. Evaluation of measurement uncertainty of the results based on an understanding of the theoretical principles of the method and practical experience of the performance of the sampling or test method.
7.2.2.1.1
Validation, or where appropriate performance checks, shall be performed on new Unit procedures, methods, equipment, and instrumentation that affect the quality of the testing in order to establish that the particular requirements for a specified intended use are fulfilled. Methods shall be validated prior to their introduction into authorized casework.
Each Unit within the CL shall ensure that all validations: a. Include the associated data interpretation;
b. Establish the data required to report a result, opinion, or interpretation;
7.2.2.2 Changes to Validated Methods
When changes are made to a validated method, the influence of such change shall be recorded and assessed. Where they are found to affect the original validation, a new method validation shall be performed. Methods shall be validated, or where appropriate performance checked, when conditions or methods have changed or reconfigured.
7.2.2.2.1
The associated data interpretation is considered part of a validated method. When changes are made, then 7.2.2.2 applies.
7.2.2.3 Specified Requirements for Customers’ Needs
The performance characteristics of validated methods, as assessed for the intended use, shall be relevant to the customers' needs and consistent with specified requirements. The validation criteria shall be defined. In order to meet customers’ needs and to demonstrate the fitness for use, the validation study may be evaluated in terms of the following criteria:
a. Limit of detection b. Limit of quantification c. Selectivity of the method d. Linearity
e. Precision
i. Repeatability ii. Reproducibility
f. Robustness against external influence and/or cross-sensitivity against interference from the matrix of the sample or test item
g. Measurement uncertainty h. Measurement range i. Bias
j. Accuracy k. Sampling
ISSUED BY: Forensic QA Manager PUBLISHED DATE: 09/24/2019 Standards for Forensic DNA Testing Laboratories.
When multiple instruments are purchased and there has been previous validation of said
instrument, a performance check shall be performed in order to demonstrate that the instrument or piece of equipment meets the same standards.
7.2.2.4 Validation Records
The CL shall retain the following records of validation: a. The validation procedures used;
b. Specification of the requirements;
c. Determination of the performance characteristics of the method; d. Results obtained;
e. A statement of the validity of the method, detailing its fitness for the intended use. Finalized validation summaries will be maintained as a controlled document in the Qualtrax document control center. Complete validation records that include supporting data will be maintained in perpetuity by the respective Unit in hardcopy or electronic format.
