A GLYPHOSATE-based weed killer has been deemed carcinogenic by a United States jury, delivering its verdict on a cancer sufferer's damages claim against its manufacturer.

The California jury was unanimous in agreeing that the 'Roundup' weed killer which resident Edwin Hardman had treated his property with for over 30 years was a 'substantial factor' in causing his non-Hodgkin’s Lymphoma.

This outcome is still being disputed by German chemicals group Bayer, which acquired the Roundup brand as apart of its $66 billion takeover of Monsanto last year – and which saw its share value drop by almost 12% following the ruling.

The next phase of the trial is due to begin on Wednesday March 27, with Mr Hardeman’s lawyers expected to present evidence allegedly showing Bayer's efforts to influence scientists, regulators and the public about the safety of its products.

However, Bayer remained defiant: “Science confirms that glyphosate-based herbicides do not cause cancer. We are confident the evidence in phase two will show that Monsanto's conduct has been appropriate, and the company should not be liable for Mr. Hardeman's cancer."

Mr Hardeman's case is actually the second to go the wrong way for Bayer – last year the company was initially ordered to pay out $289m in damages to Dewayne Johnson, a former grounds-keeper suffering from terminal cancer – an amount that was later reduced to $78m and is still on appeal.

Glyphosate's reputation has been reeling since 2015, when the International Agency for Research on Cancer concluded that the compound was 'probably carcinogenic to humans'.

However, the US Environmental Protection Agency still insists that is safe when used carefully and likewise, the European Food Safety Authority has stated that glyphosate is unlikely to cause cancer in humans.