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法医·刑侦
12
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血迹撞击角 · α = arcsin(宽/长)
Bloodstain impact angle · α = arcsin(width/length)
α=arcsin(宽/长) · 宽长比0.5→30° · 垂直90°圆/斜角细长
An angled droplet leaves an elliptical stain; its width:length ratio recovers the impact angle
血源区 · h = d·tan(α)
Area of origin · h = d·tan(α)
反投影汇聚 · h=d·tanα=50.3cm · 二维汇聚+三维血源
Back-project several stains to the convergence, then find the origin height above it
弹道重建 · arctan(Δh/Δx)
Bullet trajectory reconstruction · arctan(Δh/Δx)
两弹孔连线 · 角=arctan(Δh/Δx)=11.3° · 反延定射手
Two holes fix a straight trajectory; its vertical angle locates and back-projects the shooter
由尸体冷却估计死亡时间
Time of Death from Body Cooling
牛顿冷却 · PMI=−(1/k)ln((T体−T环)/(37−T环))=4.4h · 趋环境
Forensic Science · Newton's law of cooling
DNA 图谱随机匹配概率
DNA Profile Random Match Probability
RMP=∏位点频率=2.4e−8≈1/4170万 · 位点越多越稀 · 身份认定
Forensic Science · random match probability
血液酒精浓度(Widmark 方程)
Blood Alcohol Concentration (Widmark)
BAC=A/(r·W)−β·t=0.077 · r男0.68/女0.55 · β0.015/h · 法定限
Forensic Science · Widmark equation
火药残留与射击距离
Gunshot residue & shooting distance
残留直径随枪距增 · 接触密环/远散淡 · >1m几无 · 判射距
diameter = 5 + 20·distance (cm); farther shots spread wider and fainter
法庭玻璃比对 · 折射率(GRIM)
Forensic glass comparison · refractive index (GRIM)
GRIM浸油加热 · 匹配≤0.0001 · 窗玻璃~1.518 · 稀有RI证据强
immerse in oil & heat until the fragment vanishes to read RI; |scene−suspect| ≤ 0.0001 is a match
指纹认定 · 细节点比对
Fingerprint identification · minutiae matching
端点/分叉细节 · 12点标准 · 匹配点越多巧合越低 · 认定
≥ 12 matching minutiae → identification; more matches = higher confidence
鲁米诺血迹推定试验
Luminol Presumptive Blood Test
血红蛋白铁催化+H₂O₂蓝光 · 灵敏1:10000 · 预试假阳(漂白/铜)
Forensic Science · presumptive blood detection
法医昆虫学:最小死后间隔
Forensic Entomology: Minimum PMI
积温ADD=Σ(T−T基)天 · PMI=ADD/(T环−T基)=16.7天 · 温高发育快
Forensic Science · minimum post-mortem interval
法医毒理学:半衰期回算
Forensic Toxicology: Half-life Back-calculation
一级C=C0(½)^(t/t½) · 反推C0=C·2^(t/t½)=2.0 · 每t½减半
Forensic Science · toxicokinetic back-calculation