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Forensic science The application of science to those criminal and civil laws that are

Forensic science The application of science to those criminal and civil laws that are enforced by police agencies in a criminal justice system. Physical Evidence Any material either in gross or trace quantities that can establish through scientific examination and analysis

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Forensic science The application of science to those criminal and civil laws that are

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  1. Forensic science The application of science to those criminal and civil laws that are enforced by police agencies in a criminal justice system.

  2. Physical Evidence Any material either in gross or trace quantities that can establish through scientific examination and analysis that a crime has been committed.

  3. Trace evidence Direct evidence Prima facie evidence Circumstantial evidence Exculpatory evidence extremely small items stands on its own to prove an alleged fact evidence established by law incriminates a person helps to prove that an accused individual is not guilty Classification of Physical Evidence

  4. Corpus delicti Associative evidence establishes that a crime has been committed links suspect with the crime. Another commonly used classification of physical evidence

  5. Physical evidence utilization in other areas of forensic investigation • Provides investigative leads for a case • Ties one crime to a similar crime or connects one suspect with another • Corroborates statements from witnesses to or victims of a crime

  6. The elements of a crime help to determine what will be useful as evidence. Besides knowing what types of evidence to search for, it is necessary to know where evidence is most likely to be found.

  7. Class characteristics Individual characteristics features that place the item into a specific category features that distinguish one item from another of the same type Characteristics of evidence

  8. Types of physical evidence • BODY FLUIDS • Conventional serology: • presence of blood in stains • species identification and ABO grouping • is not adequately informative to positive identify a person • DNA analysis can associate victim and/or suspect with each other or with the crime scene • BLOODSTAIN PATTERNS • additional information SEM: erythrocytes & lymphocytes

  9. BODY TISSUES organ samples collected at autopsy, including blood, urine and stomach contents DRUGS & CONTROLLED SUBSTANCES plant materials, powders, tablets, capsules toxicological analysis volatile compounds (ethanol, methanol, isopropanol) heavy metals (arsenic) nonvolatile organic compounds (drugs of abuse, pharmaceuticals) miscellaneous (strychnine, cyanide) trace drug presence, identity, and quantity Black tar heroine wrapped in cellophane Types of physical evidence

  10. DOCUMENTS examination typed, handwritten and printed materials for evidence of forgery indented writings, obliterated or altered writings, used carbon paper, burned or charred paper paper and ink analysis handwriting comparison to determine authenticity Types of physical evidence Obliterated writing examination

  11. HAIRS hairs analysis can determine morphological features DNA analysis toxicological examination FIBERS human/animal race body area cosmetic treatments method of removal (crushed, cut, burned, forcibly removed, fallen out naturally) can associate a hair to a person positive identification presence of drugs and poisons type color, composition construction Types of physical evidence

  12. Types of physical evidence Two matching hairs identified with the comparison microscope Flax fibers viewed withpolarized light

  13. FINGERPRINTS the strongest possible evidence of a person’s identity FIRE DEBRIS & EXPLOSIVES RESIDUE EXAMINATIONS identification of accelerants and explosive residues Types of physical evidence Fingerprint Matching Unburned accelerator liquid on a soot covered carpet

  14. 法医物证检材的提取、包装、送检

  15. 一、法医物证检材的概念 • 人体组织器官及碎块，毛发、指甲、骨骼和牙等 • 各种体液、分泌液、排泄物，如血液、精液、阴道分泌物、乳汁、鼻涕、痰、尿液、羊水及其斑痕

  16. 二、法医物证检材的特点 • 容易变性、变质、降解、腐败 • 环境对检材的影响 环境条件的作用使检材具有某些不确定性

  17. 三、检材的提取、保存与送检 • 3.1 检材的发现 • 3.2 检材的提取 • 3.3 检材的保存 • 3.4 检材的送检

  18. 3.1 检材的发现 • 全面、充分、仔细勘查案发现场及犯罪嫌疑人住所、活动场所、物品等 • 血液及血痕的发现：特别注意观察隐蔽部位及照明不充分的地方 • 精斑：受害人外阴部、小腿、内裤及阴道内；擦拭物、被褥及案发现场地面上 • 唾液斑：烟头、口香糖、瓜子壳等处 • 皮肤及组织碎块：指甲缝、致伤物

  19. 3.2 检材提取的一般原则 • 检材均应为直接提取 • 根据检材附着的不同载体，应用擦拭、剪切、刮削、吸敷、浸泡、锯凿、挖取等方法提取 • 分别提取，单独包装 • 详细登记 • 检材提取者必须戴手套持洁净器具取材，禁止赤手触摸检材

  20. 3.2 检材提取的一般原则（续） • 提取附近的空白材料 • 新鲜体液尽快检验，其余部分应制成纱布斑迹；人体组织应干燥或冷冻保存 • 检材应在阴凉通风处自然干燥成纱布斑迹，禁止加热烘干 • 提取的检材避免互相磨擦、冲撞及失落，易碎检材防止挤压和震动；易散失的检材严密包装

  21. 3.2.1 血液及血痕的提取 • 各种纺织物品上的遗留血痕：小件的可以整件提取；较大件的物品可以将血痕剪下送检并记录其所在部位，同时剪取血痕附近的空白织物一并送检。 • 树叶、草叶、禾杆等小载体上附着的血痕均可以整件提取送检。较大的木质类载体上的血痕，可根据载体的情况采取切削薄片状部分或锯掉端、角处等方法提有血部位的检材。 • 光滑水泥地面、铁木器具、陶瓷、金属物品等质地致密的载体上的血痕检材除附在较小、易于提取的物品上可以整件包装送检，否则均需要擦拭或刮取。 • 质地松软的载体如抄灰墙、泥土中的血痕的提取：将血痕尽量全部提取并尽可能少混带载体物质，同时需要在附近提取空白抄灰检材送材。泥土上的血痕尽量挖出带血的完整土块，勿使土块破碎，包装勿挤压冲撞。

  22. 3.2.1 血液及血痕的提取（续） • 凶器上血痕的提取一般尽量整件提取，如凶器较大可按在较硬载体上的血痕提取法提取血痕，记录提取部位并提取空白检材一并送检。 • 身体上附着的血痕的提取：在皮肤表面的血痕可以用纱线转移提取；如在指甲缝中的血痕可将指甲小心剪下送检并同时将无血的指甲剪下做空白对照；附着在头发上的血痕可连同头发剪下。 • 有关人员的对照血样的提取，可以从耳垂、指尖或静脉取血2ml。装入消毒试管内并EDTA抗凝。 • 在尸检时提取尸体血样。未腐败尸体取心腔血，腐败尸体取末梢静脉血3～5ml，装入消毒试管内；同时提取血液1～2ml涂于纱布上制成血斑。

  23. 3.2.1 血液及血痕的提取（续） • 检验鉴定亲子关系。取各鉴定人静脉血3～5ml，加EDTA抗凝。消毒试管分装，贴好标签，六小时送检。 • 冰雪上的血痕，提取带血的冰雪块，放在纱布上待其融化，干燥 • 提取血痕检材的数量，作为物证的常规血痕量应有3～5ml（血液3ml对于酶型或血清型的检验应尽量在一个月内送检，血痕量应不少于1cm2） • 在发生案件现场留下未干固的血迹，可取少量血迹加入生理盐中以便提取血细胞。

  24. 3.2.2 精斑的提取 • 衣物、被褥等各种织物及卫生纸上遗留的可疑精斑上的提取方法与相同载体上血痕的提取相同。注意做好记录并提取空白检材 • 被害人阴道内外的精斑的提取一般以用棉球擦取。提取时需注意先外后内，分段提取。检材提取后于阴凉处晾干，做好标记后送检。 • 野外强奸现场的精斑常遗留在树枝、草、禾杆等植物或土地上在植物上的取整件或取精斑遗留处的枝段送检。遗留在土地上的按遗留在土地上的血痕的提取方法提取。 • 遗留在较硬载体上的精斑提取法与血痕提取法相同。 • 涉嫌强奸的案件在送检精斑时需提取被害人、嫌疑人及有关人员（丈夫）等的检材一并送检 • 留有精斑的衣物已浸泡在水中，尚未用肥皂洗衣粉清洗，亦应提取送检；如已清洗干净可不必提取

  25. 3.2.3 唾液斑提取 • 新鲜唾液的提取：让提供唾液者清水嗽口后自视酸性果品，待唾液自然流出1～2ml，收集在洁净的试管或小烧杯内，置冰冻保存，做好标记或将提取的唾液用纱布吸敷后自然晾干 • 烟蒂唾液斑提取：发现可疑、与案件有关的烟蒂均应用镊子提取，按不同的提取部位分别装入物证袋，做好标记。 • 对可疑的用于堵嘴的手帕或衣物等均应整件提取，如有湿润部位应用彩色笔标出部位，晾干后包装；大件衣物可以剪下可疑部位并取附近处空白，做好标记。

  26. 3.2.3 唾液斑提取（续） • 对尸体或活体皮肤留有咬痕或可疑被舔吻部位，如乳头、口唇等到均可用浸湿的棉拭子或纱布擦拭，同时擦拭附近部位作为空白，晾干，装入物证袋。 • 可疑留有犯罪分子唾液的口杯茶具等均可用湿润的棉拭子擦拭其边缘部位，同样取近处空白，晾干，装物证袋。 • 含有唾液的信封口或邮票背面可疑遗留唾液斑时，对该信封和邮票整件提取，装物证袋，送检。 • 手帕、毛巾等均可留有使用人者本人的唾液，在案件中的手帕或毛巾应以整件提取，做好标记送检。

  27. 3.2.4 毛发的提取 • 毛发的提取，不管是遗留学生在何处的毛发（身上、地上、衣物上、凶器上）一经发现分别提取，装入纸袋同时做好记录。严禁不同部位毛发混在起。提取时应注意细心查找。提取动作轻柔，避免将粘附在载体上的毛发拉断，也防止毛发上的附着物擦掉。如果毛发在载体上附着较紧，有可能时将载体一同提取。 • 对照毛发最好与检材毛发取自同一部位，对照毛发的提取量一般不少于5～10根。

  28. 3.2.5 粪便的提取 • 遗留在织物及小件物品上的粪便均可以整件或将部分剪下送检，提取方法与遗留在相同载体上的血痕的提取相同。 • 遗留在地面上的粪便，完全风干的可提取50克用纸包装送检；较新鲜的未干的粪便可装入干净瓶中在冷冻环境下送检。 • 在凶杀案现场提取到粪便时，对该案的被害尸体应提取粪便。解剖时提取肠内容物工严检时经肛门提取30～50克粪便，装入干净的烧杯内冷冻保存。

  29. 3.3 检材的送检 • 法医物证检材的各种检验应在公检法、司法鉴定单位及法医专业技术部门进行。鉴定人员应具有法医师（含法医师）或相当职称以上资格 • 送检时必须有委托书，附案情材料；再鉴定或复核检验应有初检报告或鉴定书复印件 • 邮寄到各级技术部门检验的检材除公函委托外还应有检材清单 • 提取的各种检材按物证包装要求写明检材名称、部位、数量、发现地点、提取方法、提取人、送检要求

  30. 3.4 检材的保存 • 法医物证检材需装在消毒或洁净容器中或包装袋中  • 各种检材的各种斑迹均应经干燥处理，防止霉变 • 低温存放各种检材，置4℃泠存，血液置4℃冰箱 • 检材提取后应有专人负责保存，物证检材袋应加密封口 • 检材应在原办案单位保存到案件审理终结后1~2年

  31. 3.4 检验程序及要求 • 仔细核对检材的包装、种类、数量 • 判断是否能够满足送检单位的检验目的 • 尽量节省检材，如果检材量少，必须用完检材时需明确告诉送检单位 • 鉴定报告书须有2或2个以上鉴定人亲笔签名 • 送检检材应及时退还送检单位

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