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Figure 9.1
Handwriting exam.
Pattern recognition is a mandatory skill in the
practice of criminalistics. Document examiners who perform handwriting anal-
ysis are asked to discern subtle pattern similarities and differences in tests like
the one illustrated here. This is one way in which they demonstrate proficiency
in correctly concluding whether two samples originate from the same writer or
not. Which rows have matching shapes and which rows have no repeated figures?
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221
 
Good Laboratory Practice — 
Establishing Validity 
 
and Reliability
A.
Optimization ......................................................................................... 222
B.
Validation .............................................................................................. 223
1.
Levels of Validation ....................................................................... 224
2.
Validation of Methods for Comparison Evidence ...................... 225
3.
Validity vs. Reliability.................................................................... 225
4.
Is Validation Required? ................................................................. 228
C.
Quality Assurance and Quality Control.............................................. 228
1.
Quality Assurance.......................................................................... 228
2.
Quality Control ............................................................................. 228
a.
Standards and Controls ......................................................... 229
D.
Standardization ..................................................................................... 230
E.
Review.................................................................................................... 232
1.
Internal Review.............................................................................. 232
2.
Independent Review...................................................................... 233
3.
Elements of Review ....................................................................... 234
a.
What’s the Question? ............................................................. 234
b.
Documentation ...................................................................... 235
c.
What Evidence Was Tested?................................................... 236
d.
Data and Results..................................................................... 236
i. Standards and Controls ................................................... 236
ii. Second Blind Read ........................................................... 236
e.
Calculations ............................................................................ 237
f.
Interpretation and Conclusions ............................................ 237
g.
Validation................................................................................ 237
h.
The Big Picture....................................................................... 240
F.
Summary ............................................................................................... 240
References ...................................................................................................... 241
9
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222
Principles and Practice of Criminalistics
If you get to think, you have to think