Long ago (1956) and in a place far away (Denver) there lived a Federal Bureau of Narcotics agent named Marsh. Agent Marsh had a paid confidential informant named Hereford who routinely supplied information regarding violations of the narcotic laws which Marsh found to be accurate and reliable.

　　一九五六年丹佛市的联邦禁毒署特工马什通过付费方式获得了一名名为赫拉夫德的机密级特情线人的情报，该名线人按常规提供涉及毒品犯罪的信息，马什发现其提供的情况一直很准确可靠（美国相关法律中线人分级为三级）。这次的情报称：“詹姆斯 德雷普以零包贩卖方式将毒品卖给瘾君子。德雷普已乘坐火车赶到了芝加哥，但是他会于九月八号或九月九号早晨携带三盎司海洛因返回丹佛。德雷普是黑人男性，脸部肤色偏淡棕色，二十七岁，五英尺八英寸高，大约一百六十磅重，穿浅色雨衣、棕色宽松便裤、棕色鞋子。德雷普将会携带一支棕黄色拉链包，他习惯走路走得相当快。”

　　Hereford provided Marsh with the following information: "James Draper peddles narcotics to addicts. Draper has gone to Chicago by train but will be returning on September 8th or 9th in the morning and will be carrying three ounces of heroin. Mr. Draper is a black male with light brown complexion, 27 years of age, 5 feet 8 inches tall, weighs about 160 pounds, is wearing a light colored raincoat, brown slacks and brown shoes. He will be carrying a tan zipper bag and habitually walks real fast."

　　九月八日早晨马什特工到达了火车站，他密切观察了所有到站的来自芝加哥的火车。但一无所获。而在九月九日早晨，马什特工看见一人，其生理特征完全符合情报描述而且衣着也十分精确地匹配，他也是从来自芝加哥的火车下车而且走路速度也十分地快。他也携带者一个棕黄色拉链包并且也穿着雨衣。马什与另一名警官将这名男子截停下并逮捕了他，警察对这名男子实施了搜查，查获了海洛因与注射器。

　　On September 8, Marsh went to the train station in the morning and watched all the trains coming from Chicago. No luck. But on the morning of September 9, Marsh saw a person, with the exact physical attributes and wearing the precise clothing, "alight" from an incoming Chicago train and start walking fast toward the exit. He was carrying a tan zipper bag and wearing a raincoat. Agent Marsh and a police officer stopped him, arrested him and searched him (finding heroin and a syringe).