Friday, February 11, 2005

We reviewed the data for your case (State v. Defendant) using our standard Macintosh screening procedure, which employs GeneScan v3.1.2 and GenoTyper v2.5 (the same software used by the forensic DNA testing laboratory) to examine the test results. Our analysis has identified the following issues that might be important to your interpretation of the DNA evidence in this case. An expert will be able to explain the significance and implications of these findings in your particular case. Please contact us when you feel it would be helpful for us to assist with those interpretations.

All of the statements listed below about the data in your case can be verified by any competent expert who has access to GeneScan and GenoTyper software and to the data you provided to us. GeneScan and GenoTyper are proprietary software programs licensed by Applied Biosystems International.

• The reference samples of the victim, "Victim", and "Victim-C",
  • Victim displays peak height imbalance at the locus FGA. The difference in the peak heights of the 21 and 24 alleles for the FGA locus (166 and 260, respectively) could be the result of a technical artifact (such as primer binding site mutations), or be evidence of more than one contributor to that sample. 
  
  
  • Victim-C displays peak height imbalance at the locus TPOX. The difference in the peak heights of the 6 and 8 alleles for the TPOX locus (54 and 101, respectively) could be the result of a technical artifact (such as primer binding site mutations), or be evidence of more than one contributor to that sample. 
  
  
  • Victim contains peaks with a low average peak height (182 RFUs). Peaks below 150 RFUs need to be interpreted with caution. The highest peak found in the sample is 376 RFU's.
  
  
  • Victim-C contains peaks with a low average peak height (122 RFUs). Peaks below 150 RFUs need to be interpreted with caution. The highest peak found in the sample is 606 RFU's.
  
  

• The reference samples of the defendant, "Defendant", and "Defendant-C",
  • Defendant exhibits possible degradation and/or inhibition in the Yellow (slope: -12.10) dye. Degradation may be the result of aging or improper handling/storage of an article of evidence. It is detected by using linear regression to identify samples with slopes less than -8.
  
  

• The evidence samples "Cigarette" and "Cigarette-C",
  • Cigarette displays peak height imbalance at 2 loci (D18, D7). The difference in the peak heights of the 15 and 20 alleles for the D18 locus (693 and 425, respectively) and the 8 and 11 alleles for the D7 locus (541 and 374, respectively) could be the result of a technical artifact (such as primer binding site mutations), or be evidence of more than one contributor to that sample. 
  
  
  • Cigarette has electropherograms that contain a few peaks (2) with high peak heights. Peak heights above 4,000 RFU's may indicate that saturation has occurred. As a result, it may not be possible to detect otherwise significant peak height imbalances. High peak heights may also give rise to "pull-up".
  
  
  • Cigarette exhibits possible degradation and/or inhibition in the Blue (slope: -21.89), Green (slope: -32.13), and Yellow (slope: -40.65) dyes. Degradation may be the result of aging or improper handling/storage of an article of evidence. It is detected by using linear regression to identify samples with slopes less than -8.
  
  
  • Cigarette-C exhibits possible degradation and/or inhibition in the Blue (slope: -12.11) and Green (slope: -8.69) dyes. Degradation may be the result of aging or improper handling/storage of an article of evidence. It is detected by using linear regression to identify samples with slopes less than -8.
  
  

• The evidence sample "Knife Blade"
  • Is consistent with its source being a mixture of two or more individuals. Several loci (D3, vWA, FGA, D8, D21, D18, D5, D13, D7) appear to have more than two alleles. Interpretation of mixed DNA samples is challenging and attaching statistical significance to consistencies with DNA profiles of reference samples is difficult. A large number of alternative interpretations regarding potential contributors are possible.
  
  
  • Has electropherograms that contain one peak with a high peak height. Peak heights above 4,000 RFU's may indicate that saturation has occurred. As a result, it may not be possible to detect otherwise significant peak height imbalances. High peak heights may also give rise to "pull-up".
  
  

• The evidence sample "Knife Handle"
  • Is consistent with its source being a mixture of two or more individuals. Several loci (vWA, FGA, D8, D21, D18, D5, D13, D7) appear to have more than two alleles. Interpretation of mixed DNA samples is challenging and attaching statistical significance to consistencies with DNA profiles of reference samples is difficult. A large number of alternative interpretations regarding potential contributors are possible.
  
  
  • Contains peaks with a low average peak height (381 RFUs). Peaks below 150 RFUs need to be interpreted with caution. The highest peak found in the sample is 2062 RFU's.
  
  

• The evidence samples "Underwear" and "Underwear-C",
  • Underwear-C displays peak height imbalance at the locus TPOX. The difference in the peak heights of the 8 and 9 alleles for the TPOX locus (934 and 137, respectively) could be the result of a technical artifact (such as primer binding site mutations), or be evidence of more than one contributor to that sample. One of the peaks in the imbalanced locus falls below the threshold 150 RFUs, indicating that it is possibly caused by stochastic effects.
  
  
  • Underwear is consistent with its source being a mixture of two or more individuals. Several loci (D3, vWA, FGA, D8, D21, D18, D5, D13, D7) appear to have more than two alleles. Interpretation of mixed DNA samples is challenging and attaching statistical significance to consistencies with DNA profiles of reference samples is difficult. A large number of alternative interpretations regarding potential contributors are possible.
  
  
  • Underwear-C is consistent with its source being a mixture of two or more individuals. Several loci (D3, D16, THO1, CSF, D7) appear to have more than two alleles. Interpretation of mixed DNA samples is challenging and attaching statistical significance to consistencies with DNA profiles of reference samples is difficult. A large number of alternative interpretations regarding potential contributors are possible.
  
  
  • Underwear-C contains peaks with a low average peak height (324 RFUs). Peaks below 150 RFUs need to be interpreted with caution. The highest peak found in the sample is 967 RFU's.
  
  
  • Cofiler and Profiler Plus yielded inconsistent genotype information for a single sample. Underwear contains an additional peak in the D3 locus (Allele 11 - 69 RFUs). Underwear-C contains an additional peak in the D7 locus (Allele 9 - 58 RFUs). Missing or additional peaks indicate a possible problem during testing.
  
  

• The control sample "Known Blank (Run 4)"
  • Contains 1 peak. Negative or Blank Controls are used to calibrate the genetic analysis machine and contain no DNA profile. The presence of peaks is a possible indication of contamination or other problem during analysis. Review the GenoTyper electropherograms or the Genophiler Spreadsheet to see how many peaks are present and their relative peak heights. If the peaks are low (below 150 RFU's), it is possible that the peaks are simply artifacts or noise. The highest on-ladder peak found is 76 RFU's.
  
  

• The control sample "Neg Control (Run 1)"
  • Contains 1 peak. Negative or Blank Controls are used to calibrate the genetic analysis machine and contain no DNA profile. The presence of peaks is a possible indication of contamination or other problem during analysis. Review the GenoTyper electropherograms or the Genophiler Spreadsheet to see how many peaks are present and their relative peak heights. If the peaks are low (below 150 RFU's), it is possible that the peaks are simply artifacts or noise. The highest on-ladder peak found is 100 RFU's.
  
  

• The control sample "Neg Control (Run 4)"
  • Contains 3 peaks. Negative or Blank Controls are used to calibrate the genetic analysis machine and contain no DNA profile. The presence of peaks is a possible indication of contamination or other problem during analysis. Review the GenoTyper electropherograms or the Genophiler Spreadsheet to see how many peaks are present and their relative peak heights. If the peaks are low (below 150 RFU's), it is possible that the peaks are simply artifacts or noise. The highest on-ladder peak found is 71 RFU's.
  
  

• The control samples "Pos Control (Run 1)" and "Pos Control (Run 1)-C",
  • Pos Control (Run 1) exhibits possible degradation and/or inhibition in the Blue (slope: -9.73) and Yellow (slope: -11.27) dyes. Degradation may be the result of aging or improper handling/storage of an article of evidence. It is detected by using linear regression to identify samples with slopes less than -8.
  
  
  • Pos Control (Run 1)-C exhibits possible degradation and/or inhibition in the Blue (slope: -8.20) dye. Degradation may be the result of aging or improper handling/storage of an article of evidence. It is detected by using linear regression to identify samples with slopes less than -8.
  
  

• The control sample "Pos Control (Run 2)-C"
  • Contains no detected technical artifacts or evidence of contamination or mixture.
  
  

• The control samples "Pos Control (Run 3)" and "Pos Control (Run 3)-C",
  • Pos Control (Run 3) exhibits possible degradation and/or inhibition in the Yellow (slope: -10.01) dye. Degradation may be the result of aging or improper handling/storage of an article of evidence. It is detected by using linear regression to identify samples with slopes less than -8.
  
  

• The control sample "Pos Control (Run 4)"
  • Is consistent with its source being a mixture of two or more individuals. One locus (FGA) appears to have more than two alleles. The additional peaks in this sample were found to be below the threshold of 150 RFUs, indicating that they are possibly caused by stochastic effects. A mixture in a reference sample could indicate that contamination has occurred.
  
  
  • Has electropherograms that contain one peak with a high peak height. Peak heights above 4,000 RFU's may indicate that saturation has occurred. As a result, it may not be possible to detect otherwise significant peak height imbalances. High peak heights may also give rise to "pull-up".
  
  

• The control sample "Pos Control (Run2)"
  • Is consistent with its source being a mixture of two or more individuals. One locus (D3) appears to have more than two alleles. The additional peaks in this sample were found to be below the threshold of 150 RFUs, indicating that they are possibly caused by stochastic effects. A mixture in a reference sample could indicate that contamination has occurred.
  
  
  • Has electropherograms that contain a few peaks (2) with high peak heights. Peak heights above 4,000 RFU's may indicate that saturation has occurred. As a result, it may not be possible to detect otherwise significant peak height imbalances. High peak heights may also give rise to "pull-up".
  
  

• The control sample "Question Blank (Run 4)"
  • Contains 2 peaks. Negative or Blank Controls are used to calibrate the genetic analysis machine and contain no DNA profile. The presence of peaks is a possible indication of contamination or other problem during analysis. Review the GenoTyper electropherograms or the Genophiler Spreadsheet to see how many peaks are present and their relative peak heights. If the peaks are low (below 150 RFU's), it is possible that the peaks are simply artifacts or noise. The highest on-ladder peak found is 129 RFU's.
  
  

It is important to note that the DNA tests performed on any of the samples in this case give no indication as to the circumstances or time frames under which DNA was transferred to the samples that were tested. DNA profiling tests are generally not capable of distinguishing between alternative tissue sources (e.g. between DNA from blood and saliva)

We will be happy to discuss the implications of these issues with you at greater length if you feel that it would be helpful.