Running a DNA Analysis in MaSTR
To run a forensic DNA analysis in MaSTR, you apply a validated model to casework samples. This means that when you select an analysis template, you must select the template that contains the appropriate model for the sample data.
A DNA analysis in MaSTR requires, at a minimum, the following files and options:
• The analysis template.
• The (Analysis) Signal file.
• The Person of Interest Profile file.
• The queue priority.
Optionally, when analyzing a DNA mixture in MaSTR, you can also:
• Upload a Known Contributor Profile file.
• Elect to calculate the Relative Likelihood Ratios.
• Elect to calculate a random seed if you are concerned that you might be required to recreate every iteration of the DNA analysis for a court case. You can then set up another DNA analysis with the identical input ( (Analysis) Signal file, Person of Interest Profile files, and so on), specify this seed and MaSTR repeats the original DNA analysis in its entirety, step by step, exactly as it was carried out the first time.
MaSTR carries out a DNA analysis in up to 18 distinct steps, or tasks, with the number of steps that must be successfully completed dependent on the options that were selected for the analysis. For example, if the analysis model uses Elimination profiles, then Step 6, Calculate Elimination Database LRs, is a required step; otherwise, this step is not carried out. All applicable steps must be successfully carried out to analyze a DNA mixture. The table below details all the possible steps, where Steps 1 through 3 are the most likely steps for which issues occur during an analysis, in particular, Step 2.
Step # | Step Name | Step Description |
|---|
1 | Download Inputs | Download the analysis template, the required Signal file, and the required Person of Interest Profile file(s), and if applicable, the Known Contributor Profiles files. |
2 | Validate | Verify that the inputs are consistent, for example, the data and the template panel. Note: This is the most likely step for which issues occur during an analysis. |
3 | Run MCMC | Run the Markov Chain Monty Carlo (MCMC) process and calculate the expected signal (peak) heights in the samples. |
4 | Calculate LR Overall | |
5 | Calculate Likelihood Ratios |
6 | Calculate Elimination Database LRs |
7 | Extract MCMC Results |
8 | Plot Iteration Data |
9 | Plot Histograms |
10 | Plot Genotypes |
11 | Convergence Tests |
12 | Generate Convergence Plot Data |
13 | Plot Convergence |
14 | Generate Likelihood Ratio Convergence Plot Data |
15 | Plot Likelihood Ratio Convergence |
16 | Simulate Random Likelihood Ratios |
17 | Plot Simulated Likelihood Ratio |
18 | Plot Signal |
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