Sydney siege gunman's widow has DNA win in court

The widow of the Sydney siege gunman has had a crucial victory against police in court.

Amirah Droudis won't have to hand over a DNA sample, as she fights a charge of murdering Man Monis' ex-wife.

Ms Droudis is accused of killing Monis' ex-wife Noleen Hayson Pal in April 2013. 

Today police applied to obtain a mucus swab or hair sample from the the 35-year-old claiming it could directly link her to the murder.

Prosecutors said they hoped to match the DNA samples to DNA found inside Ms Droudis' handbag which also contained keys to the secure block of units where Hayson Pal was found set alight with 18 stab wounds. 

But defence lawyers argued that Ms Droudis had regularly visited the unit where Monis would pick up and drop off his children, therefore evidence of the keys being in her bag.

The magistrate agreed, denying the application. 

Ms Droudis smiled when the magistrate made his decision, nodding in approval, then thanking her lawyers who came over to the dock. 

Still the magistrate said there are reasonable grounds to think she committed an offence.

Police have compiled 20,000 pages worth of evidence.

The former hairdresser's bail was spectacularly revoked after her partner's deadly rampage.

She will again apply for bail on Monday.