Forensic Ballistics: Professional Ethics, Scientific Validity, and Complex Interpretation

This hard-level mock addresses the most demanding challenges in forensic ballistics: professional ethics under pressure, scientific validity limitations, complex evidence interpretation conflicts, and the intersection of ballistics science with justice. Every question requires critical synthesis.

Questions cover: ACE-V verification skipped under time pressure (removes quality check; higher error risk), PCAST 2016 limited foundational validity (qualified conclusions + acknowledge limitations; not invalid), miscalibrated comparison microscope post-report (re-examine + notify director + corrected report), prosecution and defence expert disagreement (explain specific features + offer technical review; no dismissal), back-of-head wound with distant pattern in self-defence claim (consistent with range; inconsistent with face-to-face; document for court), single LEA with 3 striations as insufficient for identification (limited features = inconclusive; not identification), institutional bias when examiner's colleague is suspect (assign independent examiner), prior inconclusive vs current identification (acknowledge both + explain basis + suggest third examination), AFTE Theory of Identification with unexplained differences in 2 of 6 LEAs (unexplained differences prevent identification regardless of agreeing LEAs), defence error rate challenge (acknowledge limited data + cite existing studies + explain methodology not invalidated), professionally altered serial number on police armoury firearm (report immediately + flag chain of custody + do not proceed), probabilistic estimate request in firearms examination (no validated framework; categorical conclusions only), re-examination with new 3D imaging technology reaching identification after original inconclusive (transparent reporting of both findings + technology difference), ejection pattern and shooter handedness claim (ejection geometry is firearm-dependent not handedness-dependent; challenge scientifically justified), pre-examination photograph as contextual bias risk (minimise case context to preserve objectivity), 100% certainty language in court testimony (overstates methodology; no zero error rate demonstrated), old ammunition headstamp discrepancy with modern ammunition on suspect (note and investigate; does not affect comparison), new alibi exoneration vs prior identification (investigate conflict; do not unilaterally withdraw; alibi does not prove forensic error), 4 of 6 LEAs agreeing but 2 with significant unexplained differences (AFTE standard requires absence of unexplained differences; inconclusive), pressure to 'be conservative' from FSL Director (report to oversight body; apply standard methodology), barrel wear after five years of continued use (original test fires captured contemporaneous state; current state irrelevant), smooth-bore katta forensic linkage possibilities (no striation comparison; use bore marks + cartridge case + wad), lost GSR stub chain of custody failure (irreplaceable; disclose fully; resampling meaningless), fireworks as GSR alternative source (assess chemistry + morphology + fireworks profile; if indistinguishable cannot exclude), private commission outside official channels to SFSL examiner (decline; route through proper channels), bullet consistent with two models under pressure to report only one (report both; class characteristics must be fully reported), wrong barrel used in comparison through exhibit mix-up (identification void; re-examine with correct firearm; cannot stand), and ambiguous staged suicide vs genuine suicide (report consistent + inconsistent findings; do not force a conclusion).

Topics covered:

• Professional ethics and independence: time pressure, senior official pressure, prosecutor language coaching, private commission, investigator direction on reporting, institutional conflict of interest
• Scientific validity: PCAST findings, 100% certainty language, probabilistic estimates, error rate challenges, feature sufficiency
• Complex interpretation: AFTE unexplained differences, GSR in occupationally exposed individuals, fireworks alternative, wound location vs range, ejection handedness inference
• Quality and process: miscalibration, comparison documentation, ACE-V verification, peer review for disagreement, barrel wear over time
• Chain of custody and integrity: altered serial number, lost GSR stub, exhibit mix-up, post-conviction review
• Post-conviction issues: new technology re-examination, alibi vs forensic finding, staged suicide ambiguity

Each question cites Saferstein's Criminalistics, NAS 2009, and PCAST 2016. Allow 30 minutes.