以亲属DNA为线索：多年尘封凶案昭雪（观点，中英对照）

在肯尼斯·史密斯（Kenneth Smith）去世后，多伦多警方近日宣布，已确认他是安省上世纪八九十年代三起悬案凶杀案的疑似凶手。这一案件的突破既非来自新的目击证人，也不是源于尘封已久的供词，而是得益于一种在当年案件发生时尚不存在的技术——亲属基因刑侦技术（investigative genetic genealogy）。

When Toronto police announced that they had posthumously identified Kenneth Smith as the suspected killer behind three Ontario cold-case murders from the 1980s and 1990s, the breakthrough did not come from a new witness or a long-buried confession. It came from a technique that did not exist when the crimes were committed: investigative genetic genealogy.

死于2019年的史密斯当时并非完全逃脱了警方的视线。 1976年，他被判强奸和绑架一名14岁女孩罪成，并之后因非法持枪而被判入狱。然而，史密斯与1997年犯下的最后一宗凶杀案，而当时加拿大国家DNA数据库（2000年）以及性犯罪者登记制度（2004年）尚未建立。

Smith, who died in 2019, had not been invisible to police. In 1976, he was convicted of raping and kidnapping a 14-year-old girl and later served prison sentences for weapons offences. But his criminal record predated both Canada’s National DNA Data Bank, established in 2000, and the sex-offender registry, created in 2004. By the time those systems were in place, Smith’s last known murder had already occurred in 1997.

数十年来，警方始终未能将从克里斯汀·普林斯（Christine Prince）、克莱尔·萨姆森（Claire Samson）和格雷斯琳·格林尼奇（Gracelyn Greenidge）三起案件犯罪现场采集的DNA，与任何嫌疑人建立起匹配。相关的科学技术虽早已存在，但当时尚缺乏能够跨越司法辖区、跨越世代进行信息比对与串联的制度和基础设施。直到2025年，调查人员终于成功解析出一组高度复杂的混合DNA样本，并将其上传至 FamilyTreeDNA，一家主要供公众寻找亲属、追溯家族血缘的私人家谱数据库，案件才由此出现转机。

For decades, DNA collected from the crime scenes involving Christine Prince, Claire Samson, and Gracelyn Greenidge sat unmatched. The science existed, but not the infrastructure to connect offenders across jurisdictions or generations. That changed in 2025, when investigators were finally able to deconvolute a complex DNA mixture and upload it to FamilyTreeDNA, a private genealogy database commonly used by people searching for relatives and ancestry.

与依赖于犯罪现场DNA与已知嫌犯之间的“精确匹配”的传统法庭DNA比对不同，亲属基因刑侦技术采取的是一种间接的迂回路径。警方首先依据犯罪现场的DNA寻找所谓的“部分匹配”，即在DNA中仅共享少量片段的个体，而这种共享程度在遗传学上通常意味着彼此只是远亲关系，例如堂表兄弟姐妹。随后，调查人员利用出生证明、婚姻登记、讣告和住址等公开资料，重建相关家族谱系。通过对年龄、性别、地理位置以及作案可能性等因素逐步筛选，警方得以锁定潜在嫌疑人，而其身份最终仍须通过独立证据或直接DNA比对加以确认。

Unlike traditional forensic DNA matching, which looks for an exact match between crime-scene DNA and a known offender, investigative genetic genealogy works indirectly. Police search for partial matches—people who share small segments of DNA consistent with being distant relatives, such as cousins. From there, investigators reconstruct family trees using public records such as birth certificates, marriage registrations, obituaries, and addresses. By narrowing the pool through age, sex, geography, and opportunity, police may identify a likely suspect, whose identity must then be confirmed through independent evidence or direct DNA comparison.

这一刑侦方法最早在2018年引发广泛关注。当年，美国调查人员利用家谱基因数据库，在案件发生数十年后锁定了被称为“金州杀手”的嫌犯。在该案中，警方并未直接找到凶手本人的DNA，而是通过一些他从未谋面的家族成员，发现了指向他的遗传线索。这些成员多为相当于二、三代的表亲，他们曾都为追溯家族血缘或寻找亲属而将自己的DNA上传至公共家谱数据库。未曾料到的是，这些零散的DNA片段使调查人员得以追溯到19世纪的一位他们共同的曾祖先，并通过细致而漫长的家谱分析，最终一步步将范围缩小至一名个名为约瑟夫·詹姆斯·德安杰洛（Joseph James DeAngelo）的个人。

This approach first gained public attention in 2018, when U.S. investigators used genealogy databases to identify the so-called Golden State Killer decades after his crimes. In that case, police did not find the offender’s DNA, but uncovered genetic links pointing back to him through people he had never met. Those links came from  family members—roughly equivalent to second or third cousins—who had uploaded their distantDNA to a public genealogy database to trace family roots or find unknown relatives. Unbeknown to them, those shared DNA fragments allowed investigators to trace a common ancestor dating back to the 19th century and, through painstaking genealogical work, narrow the search to a single individual: Joseph James DeAngelo.

自那以后，亲属基因刑侦技术已在全球范围内协助侦破了数百起悬案。研究人员估计，在北美地区，有愈 70% 的欧洲裔人士 即便从未提交过自己的DNA，也可能通过其亲属在家谱数据库中的记录而被识别出来。

Since then, investigative genetic genealogy has been used to solve hundreds of cold cases worldwide. Researchers estimate that more than 70 per cent of people of European descent in North America could now be identifiable through a relative in a genealogy database, even if they have never submitted DNA themselves.

在这一领域中，FamilyTreeDNA 对警方破案来讲具有独特优势。与 AncestryDNA 和 23andMe 等通常仅在法院命令下才允许执法机构进行基因比对的公司不同，而FamilyTreeDNA 则允许警方直接打开那些已经用户同意用于执法比对的个人资料。正是这种“自愿加入”的机制，使该公司成为多起悬案调查中的关键工具，其中也包括史密斯一案。

FamilyTreeDNA occupies a distinctive position in this landscape. Unlike companies such as AncestryDNA and 23andMe, which prohibit law-enforcement matching except under court order, FamilyTreeDNA allows police access to profiles from users who have opted in to law-enforcement matching. That opt-in framework has made the company a key tool in cold-case investigations, including the Smith case.

警方对肯尼斯·史密斯身份的确认，为那些等待了数十年的受害者家庭带来了迟来的答案，也凸显出科技进步正在重塑刑事调查的方式。与此同时，这一案件揭示了一个当代现实：即便个人并未主动同意接受监控，但由于生物学本身所具有的共享性，隐匿身份正变得愈发困难。随着亲属基因刑侦技术的日益普及，其应用所引发的法律与伦理边界问题，仍将悬而未决，并持续受到关注。

The identification of Kenneth Smith brings long-delayed answers to families who waited decades for clarity, even as it highlights how advances in science are reshaping criminal investigations. It also underscores a modern reality: anonymity is becoming harder to preserve, not because individuals consented to surveillance, but because biology itself is shared. As investigative genetic genealogy becomes more common, the legal and ethical boundaries surrounding its use are likely to remain an open—and closely watched—question.