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Murderers desperate to get rid of evidence might want to consider using bleach to wash away stains. But not just any bleach will do. When old-school chlorine-based bleach is splashed all over blood-stained clothing, even if the clothes are washed ten times, DNA is still detected.

So for the criminal aspiring for perfection, here’s the secret you’ll need to know: It’s the oxygen-producing detergents that will get rid of any incriminating evidence for good.

Researchers at the University of Valencia tested oxygen bleach on blood-stained clothing for two hours and found that it destroys all DNA evidence. Forensic tests such as luminal tests rely on the ability of blood to uptake oxygen: A protein in the blood called hemoglobin (responsible for transporting oxygen throughout the body) reacts with hydrogen peroxide and gives a positive test result.

Chlorine-based detergents contaminate blood, but leave behind intact hemoglobin. However, detergents such as Reckitt Benckiser’s Vanish produce oxygen bubbles, which cause the blood to degrade and no longer uptake oxygen.

Hopefully, anyone actually contemplating cleaning up bloodstains isn’t reading this.

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