A court ruling that means police took nearly 3700 DNA samples illegally during criminal cases has prompted a call for a law change.
Law Commissioner Donna Buckingham is now reviewing the rules about how police obtain and use DNA evidence, saying they are currently too complicated.
The call comes after the Court of Appeal found police had used an incomplete template form when getting the DNA of accused robber Ian Toki in 2011.
The form failed to make clear several rights the then-17-year-old had "without explanation".
Police have since said 3677 people had their DNA taken using the same faulty form between September 2010 and August 2014 - making them all unlawful, according to the Law Commission.
Ms Buckingham said taking DNA involved a significant invasion of privacy.
"DNA contains a huge amount of personal information. It is therefore important that the Criminal Investigations Act 1995 is clear and protects people's rights," she said.
The commission is calling for public input into the review.