The Issue
Louisiana is building a new $100 million state crime lab in Baton Rouge, 90,000 square feet, expected to open late this year. East Baton Rouge became the first sheriff’s office in the country to put a technology called Rapid DNA directly into the booking process, working with the FBI.
Officials have hinted the new lab will also bring familial DNA searching and investigative genetic genealogy into more routine use. Those three phrases get thrown around like they mean the same thing. They do not.
I built my forensic DNA background the hard way, as a trial attorney who went back for a master’s degree in Forensic DNA and Serology so I could cross-examine the state’s own analysts on their own science and assist other attorneys in meeting the difficult challenge of forensic DNA evidence.
I want to walk you through what each of these technologies actually does, where the science is solid, and where it still has real limits your defense should be built around.
Background: What’s Actually New in Louisiana
The current Louisiana State Police Crime Lab has been straining under its caseload for years. The new Baton Rouge facility is meant to fix that, with more capacity for DNA analysis, toxicology, ballistics, and digital forensics, and enough physical space to bring in the newer techniques I am about to explain.
Separately, East Baton Rouge Sheriff’s Office has already started using a Rapid DNA machine, about the size of a desktop computer, right at the booking desk. An officer takes a cheek swab. In under two hours, the machine returns a result and checks it against the Combined DNA Index System, or CODIS, the FBI’s national DNA database.
That sounds like magic. It is not magic. It is the same underlying chemistry a full crime lab has used for decades, just miniaturized and automated. Understanding that chemistry is the only way to understand where Rapid DNA is trustworthy and where it is not.
How DNA Profiling Actually Works, in Plain English
Forensic DNA analysis does not read your entire genome. It looks at 20-24 specific locations on your DNA, called short tandem repeat loci, or STR loci. At each of those spots, your DNA has a short sequence that repeats itself a certain number of times, and the number of repeats varies from person to person. Think of it like checking twenty specific addresses in a massive city, and at each address counting how many identical houses are lined up in a row. You are not touring the whole city. You are counting houses at twenty fixed stops, and the count at each stop is different enough between people that, put together, the twenty numbers create a profile that is, for practical purposes, unique to you or your identical twin.
To see those repeat counts, the lab first has to make enough copies of that DNA to actually measure it. A few cells do not contain enough DNA to analyze directly. So the lab runs a process called polymerase chain reaction, or PCR. Picture a molecular photocopier. PCR takes the tiny amount of DNA at those twenty addresses and doubles it, over and over, in cycles, until you have millions of copies. That is the amplification step, and it is what makes it possible to build a profile from something as small as a few skin cells left on a doorknob.
Once you have enough copies, the lab has to sort them by size to read the repeat counts. That happens through capillary electrophoresis. Picture a narrow glass tube filled with a gel-like material, with an electric current pulling the DNA fragments through it. Smaller fragments slip through faster. Larger fragments lag behind. Sort by size, and you can read off exactly how many repeats are at each of the twenty addresses, for both the crime scene sample and any reference sample you are comparing it to. That comparison, address by address, is what produces a match statistic in a traditional DNA case.
This whole process, done properly in a full crime lab, takes anywhere from a day to several weeks depending on lab backlog, sample complexity, and how many other cases are ahead of yours in the queue. It includes quality control checks at every stage, and a trained analyst reviewing the data before anyone calls it a match.
What Rapid DNA Actually Changes
Rapid DNA machines run the same PCR and capillary electrophoresis chemistry I just described. The difference is that it is all packed into a self-contained cartridge, run by a machine instead of a technician working the bench by hand, and compressed into roughly ninety minutes instead of days. The best analogy I can give you is a coffee pod machine versus a trained barista pulling a shot on a commercial espresso machine. Both use the same basic process, hot water under pressure through ground coffee. The pod machine is faster and requires no expertise to operate. But a barista working a complicated order, a burnt bean, an inconsistent grind, notices problems and adjusts. The pod machine does not notice anything. It runs the same automated cycle regardless of what you feed it.
That distinction matters enormously in forensic DNA work. Rapid DNA platforms have primarily been validated and approved by the FBI for direct CODIS upload – for reference samples only: a clean cheek swab from one known, cooperative person at booking. That is a straightforward sample. One contributor, high quantity, high quality DNA. The pod machine handles that fine.
What Rapid DNA has not been broadly validated for is the kind of evidence that actually gets contested at trial: degraded DNA, low-quantity DNA, low-copy DNA, or mixtures where more than one person’s DNA is present on the same swab. Mixture interpretation is hard even for a full lab with a trained analyst and modern probabilistic genotyping software. It requires judgment calls about how many contributors are present, and how to weigh partial or overlapping peaks in the data. An automated ninety-minute cartridge is not built to make those judgment calls. If your case involves DNA collected outside the clean, single-source booking context, the fact that a Rapid DNA machine produced a fast answer does not mean that answer went through the same scrutiny a complex sample requires.
The constitutional foundation for taking a DNA swab at booking, without a warrant, comes from the United States Supreme Court’s 2013 decision in Maryland v. King, which treated a cheek swab at booking as a legitimate identification procedure, similar to fingerprinting, for people arrested for serious offenses. That case involved a standard lab process on the back end, not a ninety-minute on-site machine feeding results straight into a database before a magistrate has necessarily reviewed the arrest. If DNA taken at booking in your case became evidence used against you for something beyond simple identification, that is worth close examination.
Familial Searching and Investigative Genetic Genealogy Are Not the Same Thing
These two terms get used interchangeably in news coverage, and they should not be, because they rely on completely different technology.
Familial DNA searching happens inside CODIS itself, using the same twenty STR addresses I described earlier. If a crime scene profile does not produce a direct hit, some jurisdictions will deliberately search for a partial match, someone whose twenty numbers are close to, but not identical to, the crime scene profile. A close partial match suggests a biological relative of that person might be your actual suspect. Think of it like looking at a photograph and thinking, that’s not the man I’m looking for, but he has the same nose and jawline as my suspect’s brother. It’s a resemblance, not a match, and it points investigators toward a family, not an individual.
Investigative genetic genealogy, often called IGG, is a fundamentally different technology. Instead of reading twenty STR addresses, IGG reads hundreds of thousands of locations across the genome, called single nucleotide polymorphisms, or SNPs. That is not counting houses at twenty city addresses anymore. That is scanning the entire city block by block for a much finer-grained genetic fingerprint. Investigators take that expanded profile and upload it to consumer genealogy databases, the same kind of platform people use for home ancestry kits, to find genetic relatives, sometimes distant cousins, who voluntarily uploaded their own DNA for family history research. From there, investigators build out a family tree and work forward to identify a suspect.
The genetic privacy question IGG raises is real and distinct from familial searching. A person who never had their DNA taken by police, and never consented to any law enforcement database, can still become the reason their distant cousin gets identified as a suspect, because that cousin’s ancestry-kit DNA happened to be searchable. As Louisiana’s new lab brings these techniques into more routine casework, expect to see more investigations that started not from a direct CODIS hit, but from a genealogical trail built off SNP data never intended for criminal investigation.
How Does This Apply in Louisiana?
If DNA evidence is part of your case, the first question my office asks is not whether there was a match (a usually misused word, but appropriate here – the proper word in concordance, but that is best reserved for another article). It is which pathway produced that evidence, because each pathway has a different validation record and a different set of challenge points. Was the sample run through the full Louisiana State Police Crime Lab process, with an analyst’s bench notes and a probabilistic genotyping report available for review? Was it run through a Rapid DNA machine at booking, and if so, was it a clean reference swab or something closer to crime scene evidence? Did the investigative lead in your case originate from a direct CODIS hit, a familial search, or investigative genetic genealogy built off a consumer database?
Louisiana law authorizes DNA collection from certain arrestees and convicted offenders for inclusion in the state database, consistent with the framework upheld in Maryland v. King. That authority is well established for identification purposes. What is far less settled, and what your defense should scrutinize closely, is the validation record behind whatever specific technology actually produced the number the state wants to put in front of a jury. A twenty-year-old, court-tested STR methodology and a ninety-minute cartridge machine are not interchangeable just because they both end in the letters D, N, and A.
If your case involved a genealogical lead, demand the full investigative file behind it, not just the eventual CODIS confirmation. The genealogy work that pointed investigators toward a suspect in the first place deserves the same scrutiny as any other piece of evidence that shaped the direction of the investigation.
Frequently Asked Questions
Is Rapid DNA less accurate than traditional lab DNA testing?
For a clean, single-source reference sample, Rapid DNA uses the same core chemistry as a traditional lab and can be reliable. The concern is complex or degraded crime scene evidence, which Rapid DNA platforms generally were not built or validated to handle the way a full lab with a trained analyst can.
What is the difference between familial DNA searching and investigative genetic genealogy?
Familial searching looks for a close partial match within the existing CODIS database, using the same twenty STR markers as a standard DNA profile. Investigative genetic genealogy uses a much larger set of genetic markers, uploaded to consumer ancestry databases, to trace family trees through distant relatives who were never in any criminal database.
Can police take my DNA just because I was arrested?
The Supreme Court’s decision in Maryland v. King permits DNA collection at booking for certain serious offenses, treating it as an identification procedure similar to fingerprinting. The scope of what that DNA can be used for, and how it was processed, still matters.
If a genealogy database led police to me, does that mean I’m guilty?
No. Genetic genealogy identifies possible relatives and builds investigative leads. It is not, by itself, a courtroom match. Any DNA evidence used against you should still go through validated STR comparison and independent review.
Why does it matter which lab or method processed the DNA in my case?
Different methods have different validation studies, different error rates, and different levels of scrutiny behind them. Knowing exactly which process was used is the first step in knowing how to challenge it.
Conclusion
Louisiana’s new crime lab is going to bring faster results and more advanced techniques into ordinary casework. Faster is not automatically better, and advanced is not automatically infallible. The science behind DNA evidence is powerful when it is done right, and I built my practice around understanding it well enough to test it, holding a graduate degree in the science and years qualified as a Forensic DNA Interpretation expert in Louisiana courts. If DNA evidence is part of your case, you deserve an attorney who actually understands what happened between the swab and the number in the report, not just someone who takes the state’s report at face value.
Portions of this article were prepared with the assistance of a generative AI drafting tool. All legal and factual assertions have been reviewed and verified by counsel.