1960: My uncle is the FBI Director

Chapter 7 Ancient Applications of Fingerprint Technology

Theodore carefully took Bernie's cup, wiped it repeatedly with his clothes, and then carried the cup toward Brian's house.

He rang the doorbell, and the door was quickly opened a crack, revealing Sit's wary face.

“It’s Officer Dixon and Officer Sullivan,” he said loudly. “What’s up?”

Theodore frowned and said, "Is Anna home? We have a few questions to ask."

It's understandable that residents would be on high alert after a family annihilation tragedy in the community, but it's problematic to be so wary when the police knock on the door.

Bernie wasn't stupid; he also sensed that something was wrong with Sit. He reached for his gun holster with one hand, pulled Theodore behind him, and forcefully pushed open the door.

"Go and call Anna over. We have a few questions to ask, not just about your house, but about all the residents here. Hurry up, don't waste our time."

Bernie urged impatiently.

He already looked fierce and was big, so he didn't need to pretend to be fierce. Just putting on a tough face was enough to intimidate people.

Sit froze on the spot, his face turning deathly pale. He stammered as he was about to say something when a voice from behind stopped him.

"elder brother."

Anna walked over with a forced smile. She straightened her apron and said, "Come in. I've heard what happened to them. Is it true? It's horrible. Ask me anything, and I'll be happy to help."

As she spoke, she gave Sit a push.

Sit shuddered, came to his senses, and looked at Anna.

Anna smiled at him and said, "Brother, go to the kitchen and get some cake."

After seeing Sit off, she explained to Theodore and Bernie, "I made this according to my mother's recipe. I baked it last night, so you can have a taste."

Theodore tilted his head and asked, "Aren't you going to ask how our investigation of your mother's case is going?"

Anna asked, "How's the investigation going?"

“There’s been a major breakthrough, but I can’t tell you right now.” Theo smiled, then stared intently at Anna’s bandaged hand and asked, “What happened to your hand?”

Anna panicked a little. "Oh? I accidentally cut myself with a knife. We were planning to have steak to celebrate last night, and I accidentally cut my hand while cutting the steak."

Theodore nodded noncommittally, then pushed Bernie's cup toward him, saying, "We've been rummaging through the trash for a long time and we're a bit thirsty. Could you get me some water?"

Anna, somewhat absentmindedly, grabbed the glass and poured only half a glass of water before returning.

Theodore picked up the cup and gulped it down, then stuffed the cup into the vomit bag and got up to leave, somewhat impatiently. "Thank you for the water. It helped me a lot."

Bernie was completely bewildered by Bernie's arrival and departure. Theodore, on the other hand, was very satisfied and kept urging Bernie to drive faster.

Back at the police station, it was getting dark, and the homicide unit was bustling with activity, even busier than when they left. More data was arriving, and five hours had already passed.

Theodore didn't bother the others; he asked Bernie to prepare tape, pencils, and gauze, while he went to the forensic room.

The forensic pathologists were working on Diane and Doyle's bodies, not Porcelain and Mrs. Brian's turn yet—according to the homicide unit's rules, all resources are allocated to new cases first.

Fortunately, the fingerprints Theodore had repeatedly emphasized that afternoon had been obtained. Complete and clear, Theodore was somewhat surprised, gave the old forensic doctor a thumbs-up, and hurriedly left with the fingerprint card. When he returned to the homicide unit, Bernie had already gathered all the materials and was sitting in a chair waiting for him. Seeing him arrive, Bernie hurriedly asked, "What exactly do you want?"

“Mr. Wenner needs evidence, and I’ll give him the evidence right now,” Theodore said excitedly, then grabbed his bags and rushed into the supervisor’s office.

Wenner was startled and asked, "What's wrong?"

Theodore didn't answer, and instead told Bernie, who had followed him, to start sharpening the pencil lead. Wenner looked at Bernie, who was equally confused, but did as he was told.

After there was a small pile of pen refills, Theodore had him grind them into fine powder. Theodore then put on gloves, took out a cup, wrapped the powder in gauze, and held it about seven or eight inches above the cup.

He looked around and asked, "Mr. Wenner, are you familiar with fingerprint extraction and comparison technology?"

Before Wenner could answer, Theodore carefully flicked his wrist, and fine graphite powder fell onto the surface of the dark blue cup.

At first it wasn't obvious, but gradually more and more powder fell, as if a thin layer of black gauze was covering the cup.

Theodore stopped spreading the powder, turned the cup, and blew three short breaths. A small fan-shaped area of ​​carbon powder was blown away, and fine graphite powder adhered to the surface of the cup, forming fine patterns.

Theodore turned his head and let out a long sigh, put down the cup, cut a piece of tape, and carefully stuck it on from one side.

At this point, Wenner spoke up, "I know about fingerprint technology. Currently, various states are cooperating with the FBI to build fingerprint databases, but these databases are incomplete. The FBI's fingerprint database only contains tens of millions of fingerprints. Do you know how many people live in the United States right now?"

He asked himself the question and answered, "Two hundred million people!"

"But there are only tens of millions of fingerprints on record. To find a fingerprint from tens of millions of fingerprints, you have to pray that it is among those tens of millions. Do you understand what the probability is?"

As early as the 1930s, the FBI was already using fingerprint technology, and its first director, John Edgar Hoover, consciously had his agents collect and build a fingerprint database.

However, due to technological limitations, fingerprint matching in this era requires a person to hold the fingerprint card and observe it with a magnifying glass, then compare the feature points. At least ten feature points must match to confirm a fingerprint match.

This is a time-consuming, laborious, eye-straining, and expensive task. Although fingerprint technology has been around for a long time, it is simply unaffordable for 99.99% of cases.

From a conventional perspective, Wenner is right. Even if Felton's homicide unit spent its entire year's budget, it might not be enough to match a single set of fingerprints.

But all of this is based on a one-to-many comparison, not a one-to-one comparison.

What if we have a target fingerprint?

What if we're just comparing the similarity between two fingerprints?

Theodore nodded, turning away to avoid Wenner's saliva contaminating the fingerprints on the cup. "But what if we only need to compare the similarity of a set of fingerprints?"

Wenner opened his mouth, then gave up trying to persuade him.

Theodore didn't argue. After the tape covered all the patterns, he pressed it firmly, then peeled it off and stuck it onto a blank fingerprint plate. A fingerprint card was now made.

Because the tools were rudimentary, the fingerprints extracted were not as clear as those extracted by the forensic experts using professional tools, but they were sufficient for targeted comparison.

Theodora turned on the desk lamp, took out the fingerprints she had extracted, and compared them one by one with the fingerprint cards provided by the forensic department, explaining as she went.
"These are the fingerprints extracted from the murder weapon by the forensic team; they are very complete. The fingerprints on the cup are Anna's."

(End of this chapter)