The Fudan poisoning case, a widely publicized poisoning case, was originally not complicated.
The defendant Lin Senhao and the victim Huang Yang are both 2010 master's students of Fudan University School of Medicine, with different majors, but live in the same dormitory.
Lin was dissatisfied with Huang over trivial matters and gradually held a grudge.
At noon on March 31, 2013, Lin took the highly toxic compound left over from the experiment and stored in the laboratory——— which was identified as dimethylnitrosamine——— and brought back to the bedroom and injected into the water dispenser.
The next morning, Huang developed retching after drinking water, was admitted to the hospital for treatment, and died after 15 days of ineffective treatment.
On April 11, 2013, after receiving the report from Fudan University, the Shanghai police immediately organized a special case team to launch an investigation, and soon identified Lin Senhao as a major suspect.
Lin was summoned criminally that night, and was immediately detained and arrested.
The Shanghai Municipal Procuratorate prosecuted Lin for intentional homicide.
During the investigation and prosecution stage, Lin confessed to poisoning, but was vague about his intentions.
On February 18, 2014, the Shanghai No. 2 Intermediate People's Court sentenced Lin Senhao to death in the first instance.
After the first trial, Lin Senhao appealed and changed his defense lawyer.
During the second trial, the new defense lawyer put forward three main defenses: the poison released by Lin Senhao may not be dimethylnitrosamine;
The causal relationship between Lin Senhao's poisoning and Huang Yang's death is uncertain, because Huang Yang may have suffered from hepatitis B before his death, and the amount of poisoning may not reach the lethal amount, so poisoning may not be the only cause of Huang Yang's death;
Lin Senhao has no motive for intentional homicide, the intention is only intentional injury, and the subjective elements of the crime of intentional homicide are not met.
These three defense opinions complement each other and together constitute a relatively complete defense strategy.
In the face of the above-mentioned challenges raised by the defense, both the prosecution and the victim's lawyer continued to try to eliminate doubts in the course of the second trial based on the evidence already available or newly collected.
With the increase of evidence and cross-examination by both sides and the expansion of the scope of disputes, the "Fudan poisoning case" has become complex and suspenseful, which has also attracted media attention and heated discussions on the Internet.
When the defense lawyer disclosed his main defense reason, some media even speculated that the case would be "shockingly reversed".
On January 8, 2015, the Shanghai Higher People's Court rendered a final judgment, upholding the first-instance conviction of Lin Senhao's crime of intentional homicide.
After the final verdict, the debate around the case in cyberspace has not completely stopped.
Although many netizens applauded the verdict, there were also Lin Senhao's sympathizers who cried out his grievances, believing that many doubts in the case remained unclarified in the second-instance proceedings.
A significant number of legal and media professionals hold similar views.
On December 11, 2015, with the approval of the Supreme People's Court, Lin Senhao was executed.
As a result, the judicial organs came under great pressure from public opinion, and it took two and a half years from the filing of the case to the approval of the death penalty.
We believe that the judgments of the first and second instance and the ruling approving the death penalty in this case show that the relevant courts have a clear understanding of the possible social consequences of the judgment in this case.
However, it is precisely because the standard rule of proof expressed as "beyond reasonable doubt" has not been clearly explained in domestic theoretical and practical circles in recent years.
In practice, as long as the doubts raised by the defense are not zero in probability, it is difficult for the prosecution to use "unreasonable suspicion" as a reason for counter-defense, and the court does not dare to use this as a reason for refusing to accept the defense opinion.
In fact, this is also an important reason why the court's guilty verdict is often criticized at the evidentiary level.
Using the analysis framework proposed below, we can make a clearer analysis of whether the doubts raised by the defense lawyers in the "Fudan Poisoning Case" are "reasonable", and as an example, we hope to suggest a line of thinking with general application value for judicial practice.
Poison unknown?
In all cases involving poisoning, as long as the poison used by the offender is not common in life, it is usually extremely difficult for the appraisal institution to find out its chemical properties by relying on conventional methods such as reagent testing and item-by-item investigation.
In the "Fudan Poisoning Case", the reason why the police were able to find out that the poison was dimethylnitrosamine was due to the fact that it was not too late to obtain clues, many exhibits had not yet been lost, autopsies and other evaluations were available, a large number of witness testimony could be collected, and the above evidence was basically consistent with the defendant's confession.
In other words, the identification of the poison in the case and even the final solution are indispensable to luck.
However, Lin's defense lawyer still questioned the nature of the poison, arguing that the poison Lin put into the water dispenser may not be dimethylnitrosamine, for the following reasons:
Poisons are illegally produced and illegally sold, the production process is questionable, and the price is unreasonable, which should be regarded as counterfeit and shoddy products;
Poisons are improperly kept, too long and may have deteriorated; The inspection results of the same batch of materials are inconsistent between the two appraisal reports made by different appraisal agencies;
The water sample used as the test material is easy to use during the inspection process, and there is a possibility of contamination;
Trace amounts of dimethylnitrosamines are widely present in the environment, including drinking water, and even in the human body, so if the amount of poison cannot be determined, even if a trace amount of dimethylnitrosamines is detected in the test material, it cannot be proved that it was injected by the defendant;
The prosecution refused to present the mass spectra used to identify the poison, and the defence was unable to review the identification process.
The prosecution was led by these doubts raised by the defence and had to present-for-tat evidence or claims one by one.
But if you think about it, these doubts about the nature of the poison are extremely difficult or even impossible to eliminate, and even if the evidence continues to be collected at the request of the defense, it may not help to further the truth.
According to common sense, the insufficient technical conditions of the poison manufacturer may reduce the purity of the poison, but this affects the toxicity at best, but does not change the toxicity, and the poison with reduced toxicity is still a poison.
Similarly, the "contaminated" material is still a test material, even if the test material has been "contaminated" during the inspection process, as long as the appraisal agency considers the possibility of pollution and takes corresponding technical measures, it will not affect the reliability of the identification conclusion——— Moreover, there are very few completely "clean" materials in the real world.
As for the discrepancy between the test results of different identification agencies, it is also normal, based on the existing chemical substance identification technology, it is strange if the test results of different identification are completely consistent.
If the defense's cross-examination opinion is accepted, the prosecution can only accept the reliability of the appraisal conclusion if it takes the poison at the time of Huang Yang's poisoning as a test material for re-examination; But unless you turn back the clock, this requirement will never be met.
In reality, even if the prosecution can theoretically clarify all the conditions and all processes of dimethylnitrosamine volatilization and deterioration, it is still uncertain that the bottle of chemical that was taken by Lin Senhao and injected into the water dispenser can still maintain the standard chemical properties of dimethylnitrosamine at the moment Huang Yang drinks it.
In order to challenge the prosecution's determination of the nature of the poison, the defense also proposed that trace amounts of dimethylnitrosamines are prevalent in the environment and even in the human body.
This is not only to hedge the identification conclusion of the identification agency to detect dimethylnitrosamines from Huang Yang's urine, water dispenser and water cup, but also to force the prosecution to show a "mass spectrum".
The logic of the defense is that the detection of dimethylnitrosamines from a particular sample cannot be proven to be the result of poisoning unless the mass spectrum shows dimethylnitrosamine concentrations significantly higher than its average in the environment and body fluids.
When the prosecution refuses to produce the mass spectrum, the defense ostensibly asks for a redo of the test, but in fact asks the court to presume that there is a problem with the mass spectrum, thereby denying the reliability or even authenticity of the identification conclusion.
The defence has repeatedly emphasized that mass spectrometry is the "gold standard" for determining the nature of poisons, and its intention is to make observers, including the court, belittle or ignore a large amount of other evidence presented by the prosecution in determining the nature of the poison, including the defendant's confession, multiple witness statements, the examination report of the appraisal agency on the poison and the forensic opinion of the victim's body.
However, the "gold standard" in science is not necessarily the "true standard" in law.
When making legal decisions, judicial organs should fully consider the consequences.
Using mass spectrometry as the core evidence indispensable to accusing poisoning crimes creates dangerous incentives——— as long as potential offenders use toxic chemicals that are not common in everyday life, are not immediately fatal, and are highly volatile.
Moreover, careful cover-up after poisoning and efforts to delay the time for the police to collect qualified materials can basically ensure that the court cannot determine the nature of the poison.
Moreover, the reason why the prosecution refused to produce the mass spectra was not necessarily because of the problem with the mass spectra itself, but more likely because the mass spectra were of little significance to further prove the facts of the case when there was other evidence of the poisoning behavior and the nature of the poison.
Considering that the investigation conditions of many poisoning cases are difficult to ensure reliable examination materials, the prosecution needs to avoid creating a demonstration effect and prevent the trial of this case from forming an unspoken rule of the evidence law that "mass spectra are required for all poisoning cases".
The court should have been clear and accepted of the prosecution's intentions, and neither required the prosecution to produce a mass spectrum nor made a presumption of invalidity as requested by the defense.
Uncertain causation?
The defense lawyer raised doubts about the causal relationship between Lin Senhao's poisoning and Huang Yang's death, which involved two specific doubts.
1. The amount of poisoning does not reach the lethal amount?
Since the prosecution refused to produce a mass spectra, it was logical for the defense to make the amount of poison the focus of its defense.
The logic of the defense is that even if the poison identified by the identification conclusion is indeed dimethylnitrosamine, it is only a qualitative test in the absence of mass spectrum support, and cannot be used to determine the dose of poisoning; If the amount of poisoning does not reach the lethal amount, there are doubts about the cause of death of the victim and the defendant's criminal intent.
Based on his rough estimates, the defense argued that the dose of poison that Huang Yang had taken that had been diluted in the water dispenser would not reach a lethal amount.
Although the prosecution provided Lin Senhao's confession about the amount of poison and Huang Yang's drinking water, and the witness's testimony about the remaining amount of poison stored in the laboratory, it is impossible to determine how much water Huang Yang drank and how much dimethylnitrosamine was contained in the water he drank.
In estimating, the defense assumed that dimethylnitrosamines were evenly distributed in the water in the water dispenser, but as the victim's lawyer pointed out, this assumption contradicted the working principle of the water discharger, and if Lin's confession was true, Huang's actual dose of poison was much higher than the defense's estimate.
In fact, if there is no accurate data on the lethal amount of poison, it does not make much sense to pay attention to the amount of poison or the amount of poison taken.
The defense lawyer calculated the "lethal amount" of dimethylnitrosamine in animal experiments and Huang Yang's weight to calculate the "lethal amount" of dimethylnitrosamine taken by Huang Yang, but this calculation was unscientific.
Not only is the tolerance of laboratory rats usually much higher than that of humans per unit body weight, but in terms of determining the causal relationship between poisoning and lethality, "half of the lethal amount" is meaningless, because the tolerance of poison varies greatly between individuals.
If "half of the lethal amount" of a certain poison is used as the basis for judicial judgment of the cause of death, then even if half of the world's people die of the poison poisoning, the court cannot determine the cause of death, which is obviously absurd.
Perhaps the really meaningful data is the "minimum lethal amount" of oral intake of dimethylnitrosamines.
However, for highly toxic chemicals such as dimethylnitrosamines, which are far from people's living environments, human poisoning deaths are very rare, and the medical community has no reliable data on the minimum lethal amount.
Considering that the police did not get a clue until the 11th day after Huang Yang's poisoning, the interval was long, if the poison was highly volatile, it was fortunate that the identification agency could detect the poison from any kind of sample, and further quantitative testing was almost impossible.
However, poison is actually just a tool of crime, and the prosecution only needs to prove that it really exists and is indeed enough to cause death, even if the burden of proof in this link of the tool of crime is completed.
In the case where the act of poisoning is determined, the causal relationship between poisoning and lethality should be judged primarily by the outcome of death.
No matter how hard the prosecution tries, this verdict can only be speculation in absolute terms.
2. Multiple causes and effects?
As for the cause of Huang Yang's death, the forensic medical evaluation presented by the prosecution concluded that Huang Yang was consistent with dimethylnitrosamine poisoning, which caused acute liver necrosis and died of secondary multi-organ failure.
However, during the second trial, upon the application of the defense, the court allowed Hu Zhiqiang, a "person with specialized knowledge", to appear in court to cross-examine evidence and challenge and refute the forensic medical evaluation conclusion.
Hu Zhiqiang believes that Huang Yang died of fulminant hepatitis B, and the predisposing factor was hepatitis B virus, not dimethylnitrosamine poisoning.
Although Hu's cross-examination opinion has not been unanimously agreed by hepatology experts and has been strongly opposed by forensic experts, a very authoritative hepatology literature cited by Hu has indeed pointed out that due to virus mutations, antigen-antibody complexes, hook effects and other factors, even if the above indicators are negative, there may still be fulminant hepatitis B, but the probability is very low.
Although the hospital ruled out the possibility of hepatitis B according to DNA testing during Huang's hospitalization, and DNA testing is the "gold standard" for medical judgment of whether he is infected with hepatitis B virus, the defense still singled out the flaws, pointing out that Huang's DNA test was only done once, and the blood sample was stored for 30 hours, exceeding the normal 6 hours, so the possibility of "false negative" was not ruled out.
According to the logic of the defense, if Huang may die of explosive hepatitis B, then Lin is at most partially responsible for Huang's death, and the court should therefore also give Lin Senhao a lighter or mitigated punishment.
This logic of attribution based on causation has a high degree of acceptance in legal circles, and many discussions about this case have actually acquiesced to this logic.
It is particularly noteworthy that although the prosecution and the victim's representative vigorously refute the defense of "multiple causes and one effect" at the factual level, they have never raised any questions about this logic of attribution.
During cross-examination and court arguments, they tried to argue that the victim was in good health and had never suffered from hepatitis B, and that forensic findings and hospital expert consultations had ruled out the possibility of fulminant hepatitis B, so that poisoning was the sole cause of the victim's death.
However, this fierce confrontation between the prosecution and defense is unlikely to make "the truth clearer and clearer."
At the time of the second trial, Huang Yang's body had been cremated, and the conditions for redoing autopsies or other judicial evaluations no longer existed, and the only way out was to seek authoritative guidance from more medical experts.
However, no matter how authoritative medical experts are, they are unable to rule out the "doubts" raised by the defense about the cause of Huang Yang's death in an absolute sense.
Whether it is clinical diagnosis or forensic identification, it is based on statistical inference and empirical judgment, and due to factors such as human complexity and individual differences, misdiagnosis and misjudgment can never be absolutely eliminated.
According to clinical statistics, acute fulminant hepatitis cases account for about 0.1~0.5% of adult hepatitis cases, who can confirm whether Huang Yang's cause of death is or is not such a small probability event?
In particular, after half a month from poisoning to death, which medical expert can really explain all the changes in Huang Yang's body during this period?
In fact, the question that the prosecution should ask is, "Even if the cause of Huang Yang's death cannot be ruled out by the defense, what can be done?"
By asking such questions, the prosecution can not only get rid of its own burden of proof, but also guide the court to re-examine the logic of the defense's attribution, which is the weakness of the defense strategy in this case.
In this regard, on the contrary, many "legally illiterate" netizens can see it very clearly.
They had neither the conditions nor the interest to pay attention to the expert opinions and medical basis for Huang Yang's death, but they invariably pointed the spearhead of doubts and rebuttals at the logic of attribution proposed by the defense:
"Even if the victim does have hepatitis B? That's just a criminal poisoning a hepatitis B patient, and the defendant can't be given a lighter punishment because the victim's liver is weak!"
"In any case, if Lin Senhao had not been poisoned, Huang Yang would not have been hospitalized and would not have died of fulminant hepatitis B or drug-induced allergies."
"Can stabbing someone to death be able to argue that he did not die from a knife wound but from excessive blood loss? Can it be possible to argue that he died not from a bruise but from an organ rupture?"
These remarks are not absurd, they remind legal practitioners to carefully consider the question: even if the victim's death is indeed "multiple causes and one effect", can the defendant's guilt really be reduced?
Strictly speaking, the occurrence of any injury is multi-caused, and the death of the victim in any criminal case has its own causes.
But legal causation is different from scientific causation.
The substantive economic basis of legal causation lies in minimizing the cost of loss prevention.
Only the conduct of the parties who could have prevented the accident at a reasonable cost would be legally recognized as having a legal causal link with the consequences of the damage.
Even if Huang Yang does suffer from hepatitis B and there is a de facto causal relationship between hepatitis B and his death, as long as Huang Yang cannot avoid the consequences of his poisoned death at a reasonable cost.
Huang Yang cannot be required to cure hepatitis B in advance to improve his ability to resist poison, and this de facto causal relationship cannot be recognized as a legal causal relationship.
In the "Fudan Poisoning Case", Lin Senhao was the only party who could avoid the accident at a reasonable cost.
As a graduate student of medical school, Lin Senhao should know that there are many people in the world whose anti-toxic ability is very weak, in addition to tens of millions of hepatitis B patients, including a large number of uremia patients, heart disease patients, blood disease patients and allergy patients and countless other people with weak anti-toxic ability.
If the court mitigates or mitigates the punishment of the defendant on the grounds of "multiple causes and one effect", it creates a dangerous incentive: a potential offender will be more inclined to poison when trying to murder a weak anti-drug person, because the poison killer will have a higher probability of obtaining a lighter punishment.
As a result, hundreds of millions of patients of all kinds are at higher risk of poisoning than healthy people.