Setagaya Family Murders: DNA Left in the House Where the Killer Stayed

Symbols, traces, and my case investigation record 37

Setagaya family murder
DNA left in the house where the criminal stayed

Four Miyazawa family members in Setagaya, Tokyo were killed in the house between the night of December 30 and the dawn of December 31, 2000. The criminal did not appear to have left the scene in a hurry.

Figure 1. Around the Soshigaya Park in Setagaya — Image:

From the conclusion of this record to
It is most likely that the sole criminal observed the surroundings in advance and knew some of the family's schedule or structure of the house. However, nationality, occupation, and motivation should not be determined solely by the geographical estimate of DNA or the scope of clothing distribution. According to

Prologue: Recorded Night

After the night deepens, the data was spread on the desk. The first thing that caught my eye was not the answer, but the imbalance. Some scenes were as clear as photographs and some time zones were empty as a whole. People try to capture one clear scene and explain the whole thing, but I marked the empty section first. Mysteries arise because there are many clues, but they also arise because the distance between clues is too far.

Tokyo Metropolitan Police Agency data, the criminal left a large number of traces, including clothes, bags, knives, fingerprints and blood. It was also investigated that he ate food and used a computer in the house. Nevertheless, the contrast with domestic and foreign data did not eventually lead to identity.

I deliberately read the famous hypothesis at the end. First of all, when we encounter the conclusion, it seems that all objects and symbols exist for that conclusion. Therefore, the timetable, place, object, and original text were organized first, and the witness and interpretation were placed in different compartments. The novel-like atmosphere was drawn from the cold texture of the actual record, not from a made-up secret.

Figure 2. The geography of the incident house facing the park — Image:

Case File: What I Could Believe

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Number	Confirmed Record	Current Reliability
1	The four Miyazawa family members were killed at their home in Setagaya on December 30-31, 2000.	High
2	Abundant traces of legal science, including the criminal's blood and fingerprints, remained on the scene.	High
3	The criminal left various items such as clothes and hip bags at the scene.	High
4	After the crime, it was investigated that he stayed at home for a certain period of time and used food and computers.	Medium
5	Tokyo Metropolitan Police Agency still maintains up to 20 million yen in compensation and detailed publicly wanted data.	Medium

The reason for choosing the criminal's identity and family, the time of invasion, and the purpose of the long stay were not revealed.

Caution trap
'Unexplained' is not the same as 'supernatural', 'a huge conspiracy', and 'only this hypothesis is possible'. I didn't count the blanks as evidence.

Figure 3. The criminal's clothing released by the Metropolitan Police Department — Image:

Scene Reconstruction: Finally, the place of the certain point

was changed to the actual movement, not the stage in your head. We divided the starting point, the last check point, and the location where the item was found and calculated the minimum time required in between. When the dramatic description of later generations was removed, small and specific elements such as sound and lighting, doors and roads, paper and ink, and the spacing of symbols came forward.

The person's mind was not fixed and the action was written first. The same behavior can be caused by fear, planning, error, and fatigue. If it is a code, the same symbol can be a sound, a word, a separator, and a meaningless sign. After writing down all possible roles, he erased the roles that conflict with other records one by one.

Clue 1. Four Miyazawa family members were killed at their Setagaya home on December 30-31, 2000.

I split this sentence into three pieces first. It indicated who first checked, how close the confirmation was to the incident, and where the later interpretation was attached. Old events and codes turn into clearer stories than the original while being repeatedly cited. But clarity is not the same thing as accuracy. In my notes, I separated the direct record, the traces left by the object, and the reasoning of later generations into different colors.

This clue was then confronted with the record, "A wealth of legal science traces, including the criminal's blood and fingerprints, remained on the scene." It is not a good hypothesis if one hypothesis explains only the first sentence and avoids the second sentence. In particular, if the criminal failed to pass the question, "Is it confidence or waiting for a means of transportation?" the attractive explanation also lowered the score. I've seen clues that make the conclusion uncomfortable longer than clues that make the conclusion cool.

If you look at the clues this way, the case seems a little less dramatic. Instead, there is a boundary between how far it is clear and where it is imagined. That boundary is necessary to correct reasoning when new data are released. The most dangerous moment in the unwritten record is not when you make a false hypothesis, but when you turn the hypothesis into a sentence of fact.

Clue 2. Rich traces of legal science, including the criminal's blood and fingerprints, remained at the scene.

I split this sentence into three pieces first. It indicated who first checked, how close the confirmation was to the incident, and where the later interpretation was attached. Old events and codes turn into clearer stories than the original while being repeatedly cited. But clarity is not the same thing as accuracy. In my notes, I separated the direct record, the traces left by the object, and the reasoning of later generations into different colors.

Then, the clue was confronted with the record, "The criminal left various items such as clothes and hip bags on the spot." It is not a good hypothesis if one hypothesis explains only the first sentence and avoids the second sentence. In particular, if you fail to pass the question, "Are the items thrown away at the site prepared or daily belongings?" the attractive explanation also lowered the score. I've seen clues that make the conclusion uncomfortable longer than clues that make the conclusion cool.

If you look at the clues this way, the case seems a little less dramatic. Instead, there is a boundary between how far it is clear and where it is imagined. That boundary is necessary to correct reasoning when new data are released. The most dangerous moment in the unwritten record is not when you make a false hypothesis, but when you turn the hypothesis into a sentence of fact.

Figure 4. Hip bags and belongings left on site — Image:

Clue 3. The criminal left several items, including clothes and hip bags, at the scene.

I split this sentence into three pieces first. It indicated who first checked, how close the confirmation was to the incident, and where the later interpretation was attached. Old events and codes turn into clearer stories than the original while being repeatedly cited. But clarity is not the same thing as accuracy. In my notes, I separated the direct record, the traces left by the object, and the reasoning of later generations into different colors.

Then, this clue was confronted with the record, "After the crime, the situation of staying at home for a certain period of time and using food and computers was investigated." It is not a good hypothesis if one hypothesis explains only the first sentence and avoids the second sentence. In particular, if you fail to pass the question, "Does the park-side approach require an exploration before the crime?" the attractive explanation also lowered the score. I've seen clues that make the conclusion uncomfortable longer than clues that make the conclusion cool.

If you look at the clues this way, the case seems a little less dramatic. Instead, there is a boundary between how far it is clear and where it is imagined. That boundary is necessary to correct reasoning when new data are released. The most dangerous moment in the unwritten record is not when you make a false hypothesis, but when you turn the hypothesis into a sentence of fact.

Clue 4. After the crime, it was investigated that he stayed at home for a certain period of time and used food and computers.

I split this sentence into three pieces first. It indicated who first checked, how close the confirmation was to the incident, and where the later interpretation was attached. Old events and codes turn into clearer stories than the original while being repeatedly cited. But clarity is not the same thing as accuracy. In my notes, I separated the direct record, the traces left by the object, and the reasoning of later generations into different colors.

Next, this clue was confronted with the record, "The Tokyo Metropolitan Police Agency still maintains compensation of up to 20 million yen and detailed publicly wanted data." It is not a good hypothesis if one hypothesis explains only the first sentence and avoids the second sentence. In particular, if the criminal failed to pass the question, "Is it confidence or waiting for a means of transportation?" the attractive explanation also lowered the score. I've seen clues that make the conclusion uncomfortable longer than clues that make the conclusion cool.

If you look at the clues this way, the case seems a little less dramatic. Instead, there is a boundary between how far it is clear and where it is imagined. That boundary is necessary to correct reasoning when new data are released. The most dangerous moment in the unwritten record is not when you make a false hypothesis, but when you turn the hypothesis into a sentence of fact.

Clue 5. Tokyo Metropolitan Police Agency still maintains up to 20 million yen in compensation and detailed publicly wanted data.

I split this sentence into three pieces first. It indicated who first checked, how close the confirmation was to the incident, and where the later interpretation was attached. Old events and codes turn into clearer stories than the original while being repeatedly cited. But clarity is not the same thing as accuracy. In my notes, I separated the direct record, the traces left by the object, and the reasoning of later generations into different colors.

Then, this clue was confronted with the record, "Four Miyazawa family members were killed at the Setagaya home on December 30-31, 2000." It is not a good hypothesis if one hypothesis explains only the first sentence and avoids the second sentence. In particular, if you fail to pass the question, "Are the items thrown away at the site prepared or daily belongings?" the attractive explanation also lowered the score. I've seen clues that make the conclusion uncomfortable longer than clues that make the conclusion cool.

If you look at the clues this way, the case seems a little less dramatic. Instead, there is a boundary between how far it is clear and where it is imagined. That boundary is necessary to correct reasoning when new data are released. The most dangerous moment in the unwritten record is not when you make a false hypothesis, but when you turn the hypothesis into a sentence of fact.

Figure 5. The scene of law science collecting bloodstains and fingerprints — Image:

Put three hypotheses on the same scale The

hypothesis was not evaluated as a cool sentence. The number of clues to be explained, the number of newly requested assumptions, and the degree to which they endure the opposite evidence were written, respectively. Even if one clue is fully explained, it is not a good hypothesis if the other records have to be discarded.

Hypothesis A. A lone criminal who knows the surrounding geography and the life patterns of the house broke in after a preliminary search.

This explanation has the advantage of accepting "four Miyazawa family members were killed at the Setagaya home on December 30-31, 2000" as a relatively small family. I assumed that this hypothesis was correct and walked time and space all over again. Each time people, objects, and symbols moved to the next location, they wrote down the actions and times they needed. There must have been a hidden assumption at the point where the sentence was cut off.

The biggest weakness is that it does not fully explain "the criminal left several items, such as clothes and hip bags, on the spot." If you keep adding accomplices, coincidences, and lost things to keep the hypothesis alive, you can explain anything. However, such an explanation does not predict new clues. I only scored when two independent records pointed in the same direction, and I scored every time I called in a new exception.

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So, whether or not to adopt this hypothesis as a conclusion was judged not by atmosphere but by cost. The number of clues to be explained, the number of newly requested households, and the degree to which they endure evidence against them are listed in the same table. Novel scenes were used to show the texture of facts, but not as evidence to fill in the blanks.

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Hypothesis B. An outsider who stumbled upon the boundary between the park and the house committed the crime by mixing impulse and plan.

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This explanation has the advantage of accepting "rich traces of legal science, including the criminal's blood and fingerprints, remained on the scene" as a relatively small assumption. I assumed that this hypothesis was correct and walked time and space all over again. Each time people, objects, and symbols moved to the next location, they wrote down the actions and times they needed. There must have been a hidden assumption at the point where the sentence was cut off.

123103124

The biggest weakness is that it does not fully explain "the situation of staying at home for a certain period of time after the crime and using food and computers." If you keep adding accomplices, coincidences, and lost things to keep the hypothesis alive, you can explain anything. However, such an explanation does not predict new clues. I only scored when two independent records pointed in the same direction, and I scored every time I called in a new exception.

125104126

So, whether or not to adopt this hypothesis as a conclusion was judged not by atmosphere but by cost. The number of clues to be explained, the number of newly requested households, and the degree to which they endure evidence against them are listed in the same table. Novel scenes were used to show the texture of facts, but not as evidence to fill in the blanks.

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Hypothesis C. A person who had limited contact with one of the family members but was not captured in the investigation network committed the crime.

129106130

This explanation has the advantage of accepting "the offender left several items, such as clothes and hip bags, on the spot" as a relatively small assumption. I assumed that this hypothesis was correct and walked time and space all over again. Each time people, objects, and symbols moved to the next location, they wrote down the actions and times they needed. There must have been a hidden assumption at the point where the sentence was cut off.

131107132

The biggest weakness is that "the Tokyo Metropolitan Police Agency still maintains compensation of up to 20 million yen and detailed publicly wanted data." If you keep adding accomplices, coincidences, and lost things to keep the hypothesis alive, you can explain anything. However, such an explanation does not predict new clues. I only scored when two independent records pointed in the same direction, and I scored every time I called in a new exception.

133108134

So, whether or not to adopt this hypothesis as a conclusion was judged not by atmosphere but by cost. The number of clues to be explained, the number of newly requested households, and the degree to which they endure evidence against them are listed in the same table. Novel scenes were used to show the texture of facts, but not as evidence to fill in the blanks.

Figure 6. Computer usage history in the home — Image:

Conclusions I abandoned

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When I started the investigation, I was also drawn to the most famous explanation. It organized the case into one sentence and gave intention to everything. However, in contrast to the original record, each blank required a new coincidence. I erased the conclusion then and started again. Good reasoning is not about adding anything, but about removing unnecessary assumptions.

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This case stopped not because there was a lack of clues, but because there was no bridge connecting clues with people. I didn't tie the criminal's behavior as 'bizarre', but divided it into preparation, field adaptation, stay, and departure. It was seen that there was a mixture of prepared objects and actions that happened to be done on the spot.

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In particular, the details repeated on later articles and the Internet were separated from the source. Just because the same sentence appears in multiple places does not mean that there are multiple independent sources. We first checked the possibility that one error was duplicated. After this process, the case became less colorful, but the weight of the remaining clues increased.

Figure 7. Sand likely buried in the criminal's movement — Image:

Anti-evidence: Sentence to destroy my reasoning

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The investigation ends quickly if I gather data that upholds my conclusion. So I put the three most uncomfortable questions next to the conclusion.

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• Did the criminal stay for a long time? Did he wait for a means of transportation?
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• Whether the items dumped on the site are supplies or daily belongings,
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• Does the approach to the park require exploration before the crime?

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These questions are not decorative. It is a switch that will change its conclusion when new data comes in. The ranking of the hypotheses changes immediately when directly linked information, such as the sighting source, preserved physical evidence, comparative samples from the same author, and independent dating. On the contrary, when the word "likely" increased, the ranking did not change.

Figure 8. Floor plan dividing the breakaway path and breakaway path — Image:

Final Reasoning: I Reached

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Judgment
It is most likely that the sole criminal observed the surroundings in advance and knew some of the family's schedule or structure of the house. However, nationality, occupation, and motivation should not be determined solely by the geographical estimate of DNA or the scope of clothing distribution. According to

161126162

This conclusion is not a complete final judgment. The direction calls for the fewest assumptions in the currently disclosed records and explains the most clues at the same time. It is also clear that what comes out changes the conclusion. Reliable original records, verifiable legal science data, and independent evidence directly linking people and objects are needed.

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I do not write that the case is closed. Instead, write down how far you can close it. That boundary is the result of this investigation. The fun of mystery is not that anything is possible. It's about finding out what you can throw away among the possible explanations.

Figure 9. Tokyo Metropolitan Police Agency's public wanted flyer — Image:

Additional Survey Record 1. Redraw the timetable

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Re-open the data on the desk and cover up the conclusion this time. "Four Miyazawa family members were killed at Setagaya's home on December 30-31, 2000," he continued with a line of place and time. Unconfirmed sections were not filled by imagination but marked with blank squares. The larger the square, the lower the reliability of the hypothesis to pass through the section.

169131170

On top of it, I posted an explanation saying, "A lone criminal who knows the surrounding geography and the life patterns of the house broke in after a preliminary investigation." At first, everything seemed right, but a weak connection was revealed when the question was asked, "Is the criminal's long stay confident or waiting for means of transportation?" Hypothesis has to endure the question. If you keep making new coincidences to avoid questions, you will create, not reasoning, from that moment on.

171132172

The results obtained in this section are not confirmed criminals or complete plain texts. Instead, it became clear which explanations required fewer assumptions, and what would flip the ranking if found. Even if the case is not completed, the scope of the investigation can be narrowed. This record is intended to leave that very narrow boundary.

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Further investigation record 2. Disappeared link

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Re-expanded the data on the desk and covered the conclusion this time. The place and time remained in one line, leaving only "a rich trace of legal science, including the criminal's blood and fingerprints." Unconfirmed sections were not filled by imagination but marked with blank squares. The larger the square, the lower the reliability of the hypothesis to pass through the section.

177135178

On top of it, I posted an explanation saying, "An outsider who accidentally discovered the boundary between the park and the house committed the crime by mixing impulse and plan." At first, everything seemed right, but a weak connection was revealed when the question was substituted, "Whether the items dumped on the site were supplies or daily belongings." Hypothesis has to endure the question. If you keep making new coincidences to avoid questions, you will create, not reasoning, from that moment on.

179136180

The results obtained in this section are not confirmed criminals or complete plain texts. Instead, it became clear which explanations required fewer assumptions, and what would flip the ranking if found. Even if the case is not completed, the scope of the investigation can be narrowed. This record is intended to leave that very narrow boundary.

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Further investigation record 3. The path of movement of objects

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Re-expanded the data on the desk and covered the conclusion this time. The criminal left several items, including clothes and hip bags, on the spot, and continued to line up the place and time. Unconfirmed sections were not filled by imagination but marked with blank squares. The larger the square, the lower the reliability of the hypothesis to pass through the section.

185139186

On top of that, I posted an explanation that "a person who had limited contact with one of the family members but was not captured in the investigation network committed the crime." At first, everything seemed right, but a weak connection was revealed when the question was asked, "Does the approach to the park require exploration before the crime?" Hypothesis has to endure the question. If you keep making new coincidences to avoid questions, you will create, not reasoning, from that moment on.

187140188

The results obtained in this section are not confirmed criminals or complete plain texts. Instead, it became clear which explanations required fewer assumptions, and what would flip the ranking if found. Even if the case is not completed, the scope of the investigation can be narrowed. This record is intended to leave that very narrow boundary.

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Further Survey Record 4. Opposite Hypothesis Night

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I re-opened the material on the desk and covered the conclusion this time. "After the crime, the situation of staying at home for a certain period of time and using food and computers was investigated," he continued to line up the place and time. Unconfirmed sections were not filled by imagination but marked with blank squares. The larger the square, the lower the reliability of the hypothesis to pass through the section.

193143194

On top of it, I posted an explanation saying, "A lone criminal who knows the surrounding geography and the life patterns of the house broke in after a preliminary investigation." At first, everything seemed right, but a weak connection was revealed when the question was asked, "Is the criminal's long stay confident or waiting for means of transportation?" Hypothesis has to endure the question. If you keep making new coincidences to avoid questions, you will create, not reasoning, from that moment on.

195144196

The results obtained in this section are not confirmed criminals or complete plain texts. Instead, it became clear which explanations required fewer assumptions, and what would flip the ranking if found. Even if the case is not completed, the scope of the investigation can be narrowed. This record is intended to leave that very narrow boundary.

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Further Survey Record 5. Distance between record and memory

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I re-opened the material on the desk and covered the conclusion this time. Tokyo Metropolitan Police Agency still maintains up to 20 million yen in compensation and detailed information wanted publicly."The place and the time were lined up, leaving only one behind. Unconfirmed sections were not filled by imagination but marked with blank squares. The larger the square, the lower the reliability of the hypothesis to pass through the section.

201147202

On top of it, I posted an explanation saying, "An outsider who accidentally discovered the boundary between the park and the house committed the crime by mixing impulse and plan." At first, everything seemed right, but a weak connection was revealed when the question was substituted, "Whether the items dumped on the site were supplies or daily belongings." Hypothesis has to endure the question. If you keep making new coincidences to avoid questions, you will create, not reasoning, from that moment on.

203148204

The results obtained in this section are not confirmed criminals or complete plain texts. Instead, it became clear which explanations required fewer assumptions, and what would flip the ranking if found. Even if the case is not completed, the scope of the investigation can be narrowed. This record is intended to leave that very narrow boundary.

Figure 10. Timeline indicating a long stay after the crime — Image:

Records and references

· Tokyo Metropolitan Police — Setagaya family murder

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· Tokyo Metropolitan Police — English investigation bulletin

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※ This article is a commentary in the form of personal survey records based on public records and reliable data. I have distinguished between confirmed facts and my reasoning, and I update my judgment when a new official announcement is made. External material images were edited for some color and composition according to the permitted licensing conditions, and each image source was shown in the caption.