A 16-year-old died after he took several sips of liquid meth in front of smiling and laughing border patrol officers to prove it was “apple juice”.

Mexican high school student Cruz Velazquez was shown on CCTV footage taking the drink after he was stopped from entering the US at a border crossing.

He died within two hours of what experts called a “massive overdose”.

The officers were not reprimanded or prosecuted and are still employed today.

The footage, obtained three years later, showed the jovial behaviour of the officers and the context of the teenager’s death for the first time.

Liquid methamphetamine is a powerful and highly-addictive drug that is dissolved into an amber liquid.

Cruz was carrying two bottles, provided by a cartel in Mexico. One bottle was supposed to be black tea and the other apple juice, but both were the same colour and had a syrup-like consistency.

US Customs and Border Protection officers Adrian Parellon and Valerie Baird were later accused in a lawsuit of outrageous conduct that put the teenager’s life in jeopardy. They denied the allegations and said the teenager volunteered to drink the drugs.

The officers were also accused of failing to conduct a test on the liquid, and testing kits were available to the officers at the time.

In the footage, Ms Baird is seen to make a gesture, encouraging the boy to drink from one of the bottles, which he does. Mr Parellon then seems to make another gesture to drink from the second bottle, pushing it towards him and smiling at his colleague.

Minutes later, the officers watch the teenager take yet more sips. In total, he took four drinks.

The contents of the bottles were later found to be 100 times stronger than a typical dose of methamphetamine.

Within minutes the boy was sweating profusely and shaking as his blood pressure rose, and he was quickly unable to stand.

"What you see, I think, is a basic lack of compassion and decency toward a 16-year-old boy," his lawyer, Eugene Iredale, told ABC.

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"Almost a delight that you would see in children who just pull the wings off flies slowly, a smile when he’s being asked to drink something and being put in this position."

Within minutes of drinking from the two bottles, Cruz began to convulse on the floor, screaming in pain. He called out in Spanish, including “my heart”, “my sister”, and “my cousin”.

He was taken into custody before being rushed to hospital, handcuffed to a gurney, where he died.

Ms Baird also went to hospital on advice from her colleagues as she had a drop of the liquid meth on her fingers. She said she heard the teenager’s screams from the emergency room but denied feeling guilty that he had died.

His lawyer said he believed Cruz, from Tijuana, was hired as a mole, and paid to transport the bottles to the US, and the teenager had been told his sister would be killed if he failed to cross the border.

After a review, the US Customs and Border Protection said “no further action was warranted and the officers involved were not disciplined.”

The San Diego County’s Medical Examiner’s Office ruled that the death was accidental.

Cruz's family filed a lawsuit in a federal Californian court and settled for $1 million in March.