微观视角下湿度对粉末显现手印影响规律探究  

Microscopic Viewing into Influence of Humidity on Detecting Latent Fingerprint with Powders

作　　者：秦旗 薛静[1] 王子政[1] 陈子龙[1] 吴浩[1] 吕昱帆 李孝君[1] 刘寰[1] QIN Qi;XUE Jing;WANG Zizheng;CHEN Zilong;WU Hao;Lü Yufan;LI Xiaojun;LIU Huan(Institute of Forensic Science,Ministry of Public Security,Beijing 100038,China)

机构地区：[1]公安部物证鉴定中心,北京100038

出　　处：《刑事技术》2021年第5期471-477,共7页Forensic Science and Technology

基　　金：中央级公益性科研院所基本科研业务费专项资金项目(2019JB043)。

摘　　要：目的微观视角下探究湿度对粉末显现手印的影响规律。方法利用扫描电镜微观成像技术,观察分析不同湿度下粉末的微观形态、粉末显现不同湿度下手印的微观形态、粉末显现不同方法处理高湿度手印的微观形态。结果黑磁粉、金粉、银粉分别在相对湿度50%、30%、50%时开始出现吸湿结球现象,随湿度增加,粉末吸湿结球程度加剧,且三种粉末中金粉和银粉的吸湿结球程度最为严重;对不同湿度下手印显现,黑磁粉从相对湿度50%(金粉为30%、银粉为50%)的手印开始,随湿度增加,手印乳突花纹和小犁沟位置处粉末颗粒增多,纹线模糊,乳突纹线与小犁沟难以分辨,三种粉末中黑磁粉显现手印的纹线清晰程度最高;95%湿度下手印经在50%相对湿度环境中静置4h或吹风机吹干10min后进行粉末显现,纹线变清晰。结论1)湿度对粉末和手印都有影响,其中黑磁粉显现手印适用湿度范围为相对湿度50%以下(金粉为30%以下、银粉为50%以下);湿度影响程度排序:金粉>银粉>黑磁粉;2)降低手印所处环境湿度、加快手印表面空气流通均可减弱高湿度对粉末显现的影响。Objective To explore the influence of humidity on detecting latent fingerprint with powders from microscopic viewing.Methods Scanning electron microscopy(SEM)imaging was used to observe the micro-morphology of both the powders(gold/silver/magnetic black-based)and their developed fingerprints under different humidit y,with spec ial observation being paid into the microscopic patterns of fingerprints(95%humidity)pretreated discrepantly then developed from powders.Results The agglomeration occurred to the powders of magnetic black,gold and silver when their respective environmental humidity reached to 50%,30%and 50%,having even aggravated with the humidity increasing further.Magnetic black powder showed the least influence from its moisture absorption to result in agglomeration,with the silver’s being worse and gold’s the worst.For the fingerprints in different humidity,50%humidity-saturated fingerprints made magnetic black powder begin to have their development getting worse,wit h the 30%and 50%ones causing the similar phenomenon appearing on gold and silver powder,respectively.The inc reasing humidity led more powder particles having congregated on friction ridges and furrows,leaving fuzzy and diminishing lines finally.Yet,95%humidity-saturated fingerprints can be clearly developed after they had been placed into 50%humidity environment for 4 h or blown with hair dryer for 10 min.Among the three powders,the magnetic black demonstrated its excellence to develop distinct lines of fingerprints.Conclusions Humidity does affect the efficiency of the powder and fingerprint to develop.The suitable humidity range is below 50%,30%and 50%for the respective powder of magnetic black,gold and silver.Both gold and silver powder reveal higher sensitivity to humidity than the magnetic black.Either humidity reduction or dry-air ventilation to fingerprint can have lessened the influence of high humidity on powder development.

关 键 词：湿度 扫描电镜 手印显现 粉末 

分 类 号：DF794.1[政治法律—诉讼法学]