Chapter 29 Chapter Four

Tracy's disappearance became a cold case, hanging between the Houston Police Department and the FBI.During this period, Detective Dion and I respectively solved many cases, but we still think of this case from time to time, and think of the girl who has been wronged by Xue and the lonely mother Virginia. "In my lifetime, I hope God will allow me to investigate this case thoroughly again." This is what Dion said to me at a party. "I know, I also look forward to that day." I patted Dion who was a little drunk and said.He said what was in my heart. I have sometimes visited Tracy's mother over the years.Although the pain of losing her daughter has gradually eased in Virginia's heart, she still couldn't help shedding tears every time she saw me, and said repeatedly: "It would be great if Tracy lived until now." , she should already be married..."

In fact, we all understand that Tracy is no longer in this world, but there is nothing we can do.For more than ten years, we haven't heard any news about Tracy, and we can't find any definite evidence to prove what happened to Tracy that year. It was not until 1999 that the investigation of Tracy's disappearance was resumed after a ten-year hiatus.The unsolved case investigation team is in charge of this case, and they will analyze it from a new angle.However, Tracy's boyfriend, Michael Neal, and his brother Robert are still serving time in prison on charges unrelated to Tracy's disappearance.

In August 1999, the FBI in Houston formed a cold case investigation team, directly led by agents Roger Wedgworth and Harry Phillips, and I was also transferred to the investigation team. The investigation has reopened. It can be seen from Tracy's upbringing that Tracy is just like any other young girl.She was a girl scout, she was a mother's favorite, she went to middle school and prom like a normal kid, and did things that every kid her age would do, but then she got into drugs, no doubt This is her biggest mistake.And this drug led to the suspect Michael in this case. The investigation team first decided to conduct DNA analysis on the tissue cells extracted from the refrigerator that year, because after ten years of development in forensic science and other disciplines, we can now use some new technical means to collect evidence.This time we use the more precise "polymerase chain reaction assay".

However, after twelve long years, the tissue sample has badly decomposed.Then we had another problem, the hairs that were found at the same time were also missing. However, there is good news at the same time. We were surprised to find that the refrigerator from that year is still stored in the safekeeping room of the Ministry of Public Security.That's thanks to Dion's continued focus on Tracy's case throughout the decade. Despite the remoteness of hope, investigators decided to investigate and study the refrigerator again. Detective Harry Ficklis of the Cold Case Unit joined us in opening the refrigerator and finding it clean.But we noticed that it had been turned over on its back, so I thought there might be other clues that got away with it on the circuit board in the back of the fridge.

I used cotton swab balls to carefully wipe every corner of the refrigerator, even near the circuit boards, hoping to find new human tissue cells.Also, we've found that refrigerators or similar appliances have a lot of crevices, and if bodily fluids or the like get in, it's next to impossible to clean them thoroughly without leaving a mark. The forensic lab authenticated the swabs, but some of the managers of the forensic lab felt that they might not necessarily be able to find anything of value from the refrigerator because it had been there for too long.Moreover, the refrigerator is the same as many other unqualified evidence storage rooms. The environment there is not ideal, so it may not be able to preserve the evidence in good condition.

But my colleague Watson took a closer look at the swab and found a small patch of what looked like human skin tissue.Watson used "polymerase chain reaction analysis," in which he performed DNA analysis on the skin.Polymerase chain reaction analysis can analyze single-stranded DNA by duplicating it into identical bimolecular copies through a chain reaction.This analysis method is not only time-consuming, but also a cumbersome process.The results were dismal and our analysis failed. We tried and tested for months.One day, I learned that an FBI lab was experimenting with a new DNA test—the mitochondrial DNA test.This new technique of DNA mitochondrial testing is close to cutting-edge technology. Using this method, almost any sample can be tested, including blood, hair, traces of saliva that are invisible to the naked eye, and even those samples that have been stored for many years. This is because the characteristics of human DNA are almost different, and the same rate is less than one in a billion. Therefore, the new technology of DNA mitochondrial testing is very sensitive and effective, and practice has proved to be especially valuable for murder cases.

The FBI believes that this DNA mitochondrial testing technology will at least enable more murderers who were still at large due to the lack of scientific testing methods in the past to be brought to justice again. This news is too exciting.While traditional DNA tests use DNA extracted from the nucleus, mitochondrial tests use DNA taken from the mitochondria outside the nucleus.Although this method is not as accurate as traditional DNA testing, it is the only way to do it in some special cases. This time, I succeeded.The next thing to do is to compare it with a DNA sample from Tracy Joe himself.I found Tracy's letters from ten years ago, tried to extract her saliva from the top of the envelope, and analyzed them for DNA.However, the DNA extracted from saliva was already badly broken down.

However, we still hope that mitochondrial DNA will have a breakthrough in Tracy's case, and that is because mitochondrial DNA is mainly passed down from generation to generation through maternal relatives.This means that Tracy Joe's mitochondrial DNA and her mother's mitochondrial DNA should be completely identical in structure.Although we couldn't get a tissue sample from Tracy herself to compare to the tissue in the refrigerator, we could find her mother, and from her mother, we could get that kind of mitochondria. Tracy's mother knew our purpose and was very willing to cooperate with us to complete this work.The mitochondrial DNA from the tissue in the refrigerator matched Virginia's.

The problem now is that even if we have this strong evidence, Michael Neal will never take the initiative to confess the crime, he will not tell us the truth of the incident. However, his brother Robert offered to cooperate with the police in exchange for his early release.Robert has been in prison for so many years, I think he has realized that he has to do something, otherwise, he may spend his entire life in prison.