What Kinds of Evidence Do Police Use in Drug Lab Cases?

What Kinds of Evidence Do Police Use in Drug Lab Cases?

When police make drug arrests, they rely on evidence analyzed in crime labs to secure convictions. But what kinds of evidence do they actually use? And how reliable is it? This article will break down the main types of evidence in drug cases and discuss some of the controversies surrounding them.

Chemical Testing

The most common type of evidence is chemical testing to identify suspected drugs seized from a suspect or crime scene. Police use two main methods:

• Color tests – Simple chemical reactions that cause the substance to change color if it contains certain drugs. For example, the Scott Reagent test turns cocaine into a blue solution.
• Spectrometry – Uses an instrument to compare the molecular structure of the substance against a database of known druf profiles. Examples are infrared spectrometry, mass spectrometry, and Raman spectrometry.

Chemical tests form the backbone of most drug lab work. Their quick, inexpensive, and easy to perform. But they also have limitations. Color tests lack specificity and can confuse legal drugs with illegal ones. Spectrometry provides more definitive identification but requires expensive equipment and trained technicians.

Controversies can arise when labs misinterpret test results due to human error, sample contamination, or equipment malfunctions. There have been scandals where techs falsified results to secure convictions. Quality control and accreditation standards aim to prevent these issues but are not failsafe.

Drug Quantitation

In addition to identifying drugs, labs also measure the quantity seized. This determines the criminal charge, such as:

• Possession
• Possession with intent to distribute
• Trafficking

Police use specialized balances to weigh powder drugs to the milligram. Liquid drugs are measured by volume. Quantitation accuracy is critical, since being over the limit for trafficking versus possession carries vastly different penalties.

But measurement uncertainty means results have some range. Courts debate whether it’s fair to convict if the drug weight is near the cutoff between charges. Factors like moisture loss and trace amounts on packaging also complicate measurements.

Drug Purity Testing

Drug purity helps determine intent to distribute. Drugs in bulk for resale are often highly pure, while street-level doses are diluted. Police measure purity using chromatographic methods to separate and quantify adulterants.

But purity analysis has pitfalls. Cutting agents vary widely, making it hard to profile. Traffickers often “re-rock” or compress adulterated drugs to appear pure. And purity between batches fluctuates. So while purity provides useful evidence, it requires careful interpretation.

Fingerprint and DNA Analysis

Fingerprints or DNA on drugs, packaging, or other evidence can link suspects to a crime. Police use forensic databases to match prints and genetic profiles. This association evidence can make or break a drug case.

But contamination can mar fingerprint and DNA results. Crime scene techs must prevent transfer between evidence items. And accidental transfer between suspects in custody can cause false positives. Statistical methods calculate match probabilities, but human bias can influence interpretation.

Digital and Financial Evidence

Beyond drugs themselves, police collect supporting evidence:

• Text messages, call records, online searches about drug activities
• Security footage of drug deals
• Bank records showing suspicious cash deposits

This evidence provides context about the scale and intent of operations. But privacy rights make digital evidence hard to access. And financial evidence alone is circumstantial.

Field Drug Tests

Police also use portable drug test kits for rapid results at the scene. These involve similar color tests to the lab but have high false positive rates. Their role is preliminary screening to establish probable cause. But controversies occur when officers rely on field tests for arrests without lab confirmation.

Conclusion

In summary, drug cases rely on scientific evidence analyzed in police labs. Chemical, quantitation, and purity testing identify and characterize seized drugs. Fingerprints, DNA, and digital evidence link suspects. Field tests provide preliminary screening.

But all these methods have limitations. Precision and interpretation issues can alter outcomes. When dealing with people’s lives and liberties, drug evidence requires careful, ethical handling. Proper oversight and transparency helps ensure justice is served.

References

Houston DNA Lab Problems Put Cases in Doubt (New York Times)

Drug Crime Overview (University of Michigan Law School)

Purity of Street Drugs (DEA)

DNA Evidence Contamination (National Institute of Justice)

False Positives in Field Drug Tests (ProPublica)