New DPS labs reporting requirements

D. Pat Johnson

Deputy Assistant ­Director, Law ­Enforcement Support Division, Crime ­Laboratory Service

The Texas Department of Public Safety’s Crime Laboratories reports will look a little different from now on.

The Texas Department of Public Safety Crime Laboratories are accredited by the American Society of Crime Laboratory Directors’ Laboratory Accreditation Board (ASCLD/LAB), and the requirements of this accreditation include specifics on how crime laboratory test results are reported. Note that the DPS labs issue a total of around 100,000 reports a year.
    One new reporting requirement went into effect during 2012, and a second is expected to. These requirements specify how two testing issues shall be reported. First, laboratories are required to address how evidence items are sampled for testing. Second, laboratories must address the uncertainty of measurements of evidence when those measurements matter. This article will describe these two new areas of reporting and provide an example of how the new lab reports will appear.

Sampling of evidence
Let’s assume that the drug exhibit submitted by a police officer for testing consists of 100 small packets of white powdery material that all look alike (are homogeneous). The crime laboratory analyst may take three different approaches to testing this exhibit, all of which meet accreditation requirements:
1)    perform preliminary and confirmation tests on the contents of all 100 packets of white powder and report the findings and total net weight of the drug or drugs identified;
2)    perform preliminary and confirmation tests on one packet (or some other small number of packets) of the white powder and report the findings and net weight of the contents of only the packets tested; or
3)    employ a statistically valid sampling plan and determine the number of packets that must be tested at a 95-percent confidence level to make an inference about the whole lot of 100 packets. Then perform preliminary and confirmation testing on the contents of that number of packets. If all packets tested contain the same drug or drugs, then the appropriate inference can be made.

Uncertainty of ­measurement
Mostly the uncertainty of measurement comes into play with weighing drug evidence and with determining the concentration of alcohol in the blood of a DWI suspect. The DPS Crime Laboratories have determined this measure of uncertainty for both types of testing; the uncertainty will be reflected on the laboratory report with a +/- weight with drug items or a +/- weight per volume measure of the alcohol concentration. Sample wording of two such laboratory reports are below and on the opposite page; the sampling plan and uncertainty information is in bold text.

Controlled Substance Analysis Laboratory Report
Completion Date: April 2, 2012
Laboratory #
Suspect: Smith, John H.   
DOB 10/07/1985
Requested Analysis: Controlled Substance Analysis
Evidence description, Results of Analysis and Interpretation:
01-01 Bag of plant substance
    Marihuana  25.68 grams +/- 0.02 grams net weight

02-01  100 plastic packets of white powder
    Cocaine  17.34 grams +/- 0.02 grams net weight
10 of 100 packets were sampled for analysis. (A statistical sampling plan was used that indicates with a 95 percent confidence that at least 75 percent of the items contain the substance identified.)
This report has been electronically prepared and approved by:
Rodney Jones, Forensic Scientist
Texas DPS Crime Laboratory

 

Alcohol Analysis ­Laboratory Report
Completion Date: August 7, 2012
Laboratory #
Suspect: Doe, John H.
DOB 10/07/1991
Requested Analysis: Determination of Alcohol Analysis
Evidence description, Results of Analysis and Interpretation:
01-01 Gray top blood tube ­specimen from John H. Doe
    Contains 0.095 grams +/- 0.005 grams of alcohol per 100 ­milliliters of blood
This report has been electronically prepared and approved by:
James Andrews, Forensic Scientist
Texas DPS Crime Laboratory

If you have any questions about either of these matters, feel free to contact me at 512/424-2143 or the manager of the DPS laboratory in your area.