“smoking gun”是英语中极具画面感的名词短语，词源根植于19世纪西方侦探文学与司法场景。其字面义为“冒烟的枪”——在凶案现场，“刚开过火、还在冒烟的枪”是证明某人作案的最直接证据（枪上的指纹、硝烟痕迹可直接指向凶手，无需间接推断）。1847年，美国作家埃德加·爱伦·坡在侦探小说中首次用“smoking gun”比喻“无可辩驳的关键证据”；20世纪70年代“水门事件”中，美国媒体频繁用该短语指代“证明尼克松团队窃听的录音带”，使其成为全球熟知的流行表达，此后固定为“关键直接证据；铁证如山”的隐喻义。
其核心语义是“证明某人有罪、有错或某事实成立的，无可辩驳的直接证据；确凿证据；铁证如山”。语义关键点有三：
一是证据属性，必须是“直接证据”，区别于“间接证据（circumstantial evidence）”——前者能直接锁定事实，后者需推理；
二是证明力，具有“无可辩驳性”，一旦出现便足以证实结论，无反驳余地；
三是指代对象，仅指代“物或事实”（如录音、文件、物证），不指代“人”。该短语书面与口语通用，情感色彩中性（仅描述证据，不褒不贬），但常出现在揭露真相、司法调查、负面事件的语境中。
请看精彩例句：
The investigators finally found the smoking gun—an email in which he admitted to stealing company funds.
调查人员最终找到了关键证据——一封他承认窃取公司资金的邮件。
This memo could be the smoking gun that investigators have been looking for.
这份备忘录可能是调查人员一直在寻找的关键证据。
The search for other kinds of evidence tying him to trafficking has not produced a smoking gun.
还没有找到其他能够证明他参与了毒品交易的确凿证据。
She suspected her boyfriend was cheating, but she didn’t have the smoking gun until she saw his text messages with another girl.
她怀疑男友出轨，但直到看到他和另一个女孩的短信，才拿到确凿证据。
The politician denied taking bribes, but the media released a smoking gun: a video of him accepting cash.
这位政客否认受贿，但媒体公布了关键证据：一段他收钱的视频。
Parents couldn’t prove their child lied about homework until they found the smoking gun—his uncompleted assignment hidden under the bed.
父母一直无法证明孩子在作业上撒谎，直到找到关键证据：他藏在床底下的未完成作业。
He claimed he’d never met the woman, but the smoking gun was a photo of them together at a party last month.
他声称从未见过那个女人，但关键证据是一张上个月他们在派对上的合影。
The company argued the accident was an accident, but the smoking gun was a safety report warning of the problem six months ago.
该公司称事故是意外，但关键证据是一份六个月前就预警该问题的安全报告。
In their divorce, she needed a smoking gun to prove he’d hidden assets; she finally got it from his bank statement.
离婚时，她需要关键证据证明他隐匿财产；最终从他的银行对账单中找到了确凿证据。
The diplomat denied leaking secrets, but the smoking gun was a memo he wrote that matched the leaked information exactly.
这位外交官否认泄密，但关键证据是他写的一份备忘录，内容与泄密信息完全吻合。
Military investigators found the smoking gun: a document proving the general had ignored orders to protect civilians.
军事情报人员找到了关键证据：一份证明将军无视保护平民命令的文件。
She thought her friend had spread rumors about her, but she didn’t have the smoking gun until another friend showed her a voice message.
她认为朋友在散布她的谣言，但直到另一个朋友给她看了一条语音消息，才拿到确凿证据。
He said he’d been at home all night, but the smoking gun was his credit card receipt from a restaurant across town.
他说整晚都在家，但关键证据是他在城对面一家餐厅的信用卡消费记录。
We don’t need speculation—we need a smoking gun. Find the email that links him to the murder, and this campaign is over.
我们不需要猜测——我们需要确凿证据。找到能证明他和谋杀案有关的邮件，这场竞选就结束了。《纸牌屋》
All the clues so far are circumstantial—we need a smoking gun, something that proves he’s the killer beyond any doubt.
目前所有线索都是间接的——我们需要确凿证据，能毫无疑义证明他是凶手的东西。《神探夏洛克》
Jesse thinks Walt is lying, but he doesn’t have the smoking gun—until he sees the video of Walt admitting he poisoned Brock.
杰西认为沃尔特在撒谎，但一直没有确凿证据——直到他看到沃尔特承认毒杀布洛克的视频。《绝命毒师》
The researchers spent months looking for proof of the theory. They finally found a smoking gun: a fossil that showed the two species had lived in the same area at the same time.（2022年全国高考）
研究人员花了几个月的时间寻找这一理论的证据。他们终于找到了确凿的证据：一块化石表明这两个物种曾同时生活在同一地区。
The police said they had found the smoking gun—the video that proved the man was at the crime scene.（2025年上海中考）
警方表示，他们已经找到了确凿的证据——证明该男子在犯罪现场的视频。