A. Asking the Right Question................................................................... 246 1. Translating the Legal Question into a Science Question ........... 246 2. Formulating Hypotheses............................................................... 248 3. How Much Should an Analyst Know?......................................... 248

a. Analyst Bias............................................................................. 250 4. What Can Science Contribute? .................................................... 252

a. Can the Question Be Answered by Science? ........................ 252 b. Is the Evidence Useful? .......................................................... 253 c. Is the Test Useful?................................................................... 255 d. What Further Questions Arise as a Result of Analysis? ...... 256

B. Examination and Analysis.................................................................... 257 1. Documentation.............................................................................. 258

a. Documentation Standards..................................................... 258 2. Preserving the Integrity of the Evidence ..................................... 259

a. Prevention of Contamination ............................................... 259 b. Detection of Contamination ................................................. 259

3. Results ............................................................................................ 260 a. Analyst Judgment ................................................................... 262

4. Verification of Results ................................................................... 263 a. Blind Second Read ................................................................. 263 b. Technical Review .................................................................... 263

5. Interpretation and Conclusions ................................................... 264 a. Defining Facts and Assumptions .......................................... 264

b. Explainable Differences.......................................................... 265 c. Inference of Source vs. Inference of Contact ....................... 265

i. Inference of Source .......................................................... 265 ii. Inference of Contact ........................................................ 268

d. A Statement of Conclusion ................................................... 268 C. Summary ............................................................................................... 269 References ...................................................................................................... 271

We have finally arrived at the point in a case investigation that criminalists are most familiar with — the laboratory analysis or comparison. For a complex analysis, a good analyst may spend more time thinking about it than analyzing it. Failure to do so may result in an incorrect or suboptimal analysis, rendering useless all the good work that may have preceded it. The events and decisions surrounding the physical act of analysis share equal importance with sample processing and data collection. In this chapter we will discuss the decision-making process that occurs between the time the evidence is collected and the time the analysis is performed.