Opinion ID: 883138
Heading Depth: 1
Heading Rank: 13

Heading: Thermal Cycler

Text: Moore first challenges the thermal cycler, the heating device used in the DNA amplification process, on the following grounds: (a) the instrument was not assembled properly; (b) the brand of thermal cycler used was not the brand recommended by the manufacturer of the Cetus AmpliType Kit, (the particular PCR testing kit used in this case); and (c) AGTC used a different temperature for the denaturation phase of the DNA testing than recommended by the manufacturer of the testing kit. The sole objection Moore raises concerning the assembly of the thermal cycler is that it did not have an external monitoring system as was required by the users guide for the Perkin-Elmer thermal cycler. In response to Moore's concern that AGTC did not have an external monitoring system, Tom Wahl, the lab technician who conducted the PCR testing on the piece of brain tissue, testified that AGTC did not use the Perkin-Elmer thermal cycler but a BIOS BSC 100 thermal cycler which monitors temperature by using an internal probe. Wahl also explained that if the thermal cycler overheated the DNA sample, it could destroy the TAQ polymerase, and if the temperature was too low, there would be inadequate or no denaturation of the DNA. In response to Moore's allegation that the brand of thermal cycler was not the brand recommended by the manufacturer of the Cetus AmpliType Kit, Dr. Schanfield, the laboratory director of AGTC, testified that there was no requirement that AGTC use any specific thermal cycler. In addition, Dr. Wheeler, whose research duties include adapting the Cetus AmpliType Kit for clinical use, testified that there were a variety of thermal cyclers on the market, some of which produce similar and sometimes better results than the Perkin-Elmer Cetus machines [the machine recommended by the manufacturer]. Finally, Moore's own expert acknowledged that one reason Cetus recommended the Perkin-Elmer thermal cycler over other brands was because Cetus had a financial interest in the Perkin-Elmer machine. We conclude that Moore's challenge to the PCR evidence based on the brand of machine used did not render the PCR results inadmissible. Moore's argument that AGTC used a different temperature for the denaturation phase of the DNA testing than recommended by the manufacturer of the testing kit was also adequately explained by the State's experts. All the experts agreed that the temperatures at which the PCR process is conducted are critical. Dr. Schanfield echoed Mr. Wahl's testimony and explained that if the temperature gets too hot during the cycling procedure the TAQ polymerase would be destroyed. If the temperature does not get hot enough, the DNA will not separate and amplification will not occur. In either event, there would be no result. Moore complains that AGTC ran the denaturation phase of the PCR analysis at 93° Celsius, plus or minus two degrees, when the Cetus kit specified that the phase be conducted at a temperature of 94° Celsius, plus or minus two-tenths of one degree. Once again, Dr. Schanfield provided an adequate explanation for this difference, by stating that AGTC had to consider the elevation of its laboratory in Denver when setting the appropriate temperature for the thermal cycler.