In our drug control, urine, blood and hair tests are the three core methods of detection, divided into three levels of on-site screening, laboratory testing and laboratory re-examination. Human metabolic principles vary from one test to another, from retroactive length to judicial effectiveness. While hair tests can be traced back to six months or even years of history of drug use, well beyond conventional blood and urine tests, critical fault areas for “checking out ingredients and identifying drug use” are prevalent in the general public and even in some grass-roots law enforcement。
I. Urea, physiological limitations of blood tests: short-term metabolism, very short retrospective window periods
From the point of view of human metabolic medicine, rapid liver metabolism and kidney excretion when drugs enter the body are the core reason for the very short duration of blood and urine tests. Drug residues in the blood can be rapidly removed from degradation for a retroactive period of no more than 24 hours, reflecting only the use of drugs on that day; urine metabolites are retained for a slightly longer period, but are valid for only 3 days。
In short, after three days of drug use, the drug content in blood, urine and blood will be completely metabolized and cannot be detected again. As a result, blood and urine tests are only available for immediate drug screening in the near future and it is completely impossible to check past history of drug abuse。
Core medical principles for hair testing: solidified retention, long-lasting recording of drug use trajectory
The core advantage of hair testing stems from its unique drug perpetuating the retention of physiological properties, completely breaking down the metabolic limits of blood and urine tests, and is a core test of long-lasting trace drug use history。
After human use, the substance and its metabolites enter the blood cycle and are transported to the fur bag of the skin. In the process of longhorning of hair, the drug content is stabilized with hair horned proteins and glue proteins, permanently sequestered inside the dry, not involved in human metabolism, unable to be removed from the body, or removed from outside operations such as washing, dyeing, etc。
Hair grows at a flat rate of about 1 cm per month, and solid drug traces migrate from hair to hair. As long as the hair is not trimmed and not taken off, traces may be retained for long periods. The statutory regular retroactive cycle is six months, with enough hair to trace even years of drug abuse。
Iii. Statutory judicial criteria for hair testing: recognition of drug use as such without detection
Perceptions of the central mass of the population: hair detection of the substance is equivalent to a six-month period of drug abuse with direct punishment. However, in the light of medical tests and legal norms, the mere detection of elements does not have any positive effect on drug abuse。
The ministry of public security guidelines for the testing of hair-related samples of drug-related personnel of 2018 are the only legal basis for determination, defining the two core criteria of quantitative thresholds and timing:
The first is the concentration threshold: the common drug threshold of 0. 2 ng/mg for meth, morphine and ketamine, 0. 5 ng/mg for cocaine and 0. 05 ng/mg for cannabis. Positiveness is determined only if the detection level is above the corresponding threshold; all below the threshold is determined to be negative。
Second is the temporal retroactivity criterion: a hair positive within 3 cm is considered to be a drug use within 6 months of the sample, corresponding to the normal growth of the hair for 6 months, which exceeds the positive results in the zone and represents a history of drug abuse more than six months ago。
Core rules for judicial determination: clarifying the essential difference between “checking out components” and “testing positive”
In combination with medicine and regulations, three core rules of judicial determination can be identified to avoid miscarriage of justice:
First, check out the composition positive. Environmental dust, indirect exposure, which can cause trace contamination, is well below the legal threshold and is not a drug user; only over-detection is an effective positive result。
Secondly, reports without specific content are invalid. The mere identification of “detection of drug content”, non-value, non-threshold comparison cannot be identified as positive and cannot be used as a basis for punishment。
Third, positives need to match sampling ranges. Only three centimetres of positive drug use is allowed within six months, and old hair is positive, which is merely a mark of past drug abuse and is not a basis for current punishment。
V. Typical jurisprudence: results of drug tests not supported by concentration thresholds cannot be used as a basis for punishment
In practice, there are often miscalculations: a perpetrator is held in administrative detention for smoking e-smoking, the whole evidence is based on a population statement, and an identification report that only states that “the adb-butinaca component” is detected, without specific content and without a threshold ratio。
According to statutory norms, the test could not be considered positive and could not prove drug use within six months. At the same time, under the public security administration punishments act, a person may not be punished if he or she has made a statement without valid and objective evidence. In the end, the administrative penalty should be lifted in accordance with the law because of insufficient evidence。
Medical and legal science interpretation of drug testing thresholds
Many wonder: why do countries set extremely low detection thresholds and do not use “check out and determine”? This set of standards balances medical rigour with justice。
In the case of the threshold of 0. 2 ng/mg of meth, the ratio was only two parts per million. The very low threshold allows for a precise distinction between passive environmental contamination and active drug abuse, completely excluding no-fault interference such as environmental dust, indirect exposure, etc。
Minor residues below the threshold are not legally proven to be effective in physiochemical testing and can only be used as a reference; only the results of ultra-threshold detection can prove to be a valid residue of human active drug abuse and serve as a basis for determination。
Concluding remarks
On the whole, hair-toxing has resulted in long-activated drug use tracers based on the biological properties of hair-bearing horns, which compensate for short-term short sheets of blood and urine tests. However, law enforcement must comply with statutory standards: only positive results within 3 centimetres of detected levels above the legal threshold can determine the existence of drug abuse within six months. The simple element of detection does not have the effect of punishment, and the rules guarantee the effectiveness of drug control, the elimination of miscalculation and the combination of scientific and impartial justice。
