Sia and her estranged husband are fighting over custody of their child amid divorce proceedings — and the allegations are getting ugly.

David Bernad, an oncologist who married Sia at the end of 2022, claims in a Monday (Oct. 27) court filing that the pop star is a drug addict who cannot adequately care for their 19-month-old son, Somersault. In a Tuesday (Oct. 28) response, Sia reveals that Bernad was recently under investigation for alleged possession of child pornography.

The claims come in California divorce proceedings, which Sia initiated this past March due to “irreconcilable differences.” Bernad has since been seeking hefty spousal support from Sia, and his request for more than $250,000 a month is set for a hearing in January.

Now, Bernad is asking for full custody of Somersault (referred to by the nickname “Summi” in court documents). He alleges in the Monday filing that Sia, who has been open about her past struggles with drug addiction, is once again using.

“Sia is an unfit and unreliable parent struggling with substance abuse and addiction, rendering her incapable of providing safe or stable care for Summi,” writes Bernad in a declaration. “I am the only safe and reliable parent for our son. I am a doctor, young, healthy, and have no criminal history or drug or alcohol addiction issues.”

Bernad says he witnessed Sia abuse ketamine and opioids during their marriage, and he claims doctors found barbiturates and benzodiazepines in her system during a hospital stay last month. He says Sia should have supervised visits with Summi, and only after she’s undergone a breathalyzer test. Bernad also wants the singer to submit to random drug testing and pay him $77,000 per month in child support.

Sia, however, counters in her Tuesday court filing that she has been “fully sober for over six months” and remains committed to recovery. She says Bernad is actually the one who parties and uses recreational drugs, and that this is one of the main reasons she chose to divorce him.

“Dan’s attempt to weaponize my past sobriety journey — an issue long resolved and well-documented — serves no legitimate purpose and is intended only to distort the facts and undermine my credibility before this court,” writes Sia in a declaration. “His willingness to dredge up decades-old history to serve his own financial and strategic interests demonstrates the extent to which he will go, even at the expense of his child and the child’s mother.”

Sia says Summi should remain in her primary custody, as has been the case since this summer. According to the court filings, Bernad agreed to this arrangement — including a stipulation that his own visits be supervised — because he was under investigation for alleged child pornography found on his computer hard drive in July.

Bernad “vehemently” denies any wrongdoing and claims Sia “planted” this illicit material on his hard drive. The Los Angeles Police Department and the city’s Department of Child and Family Services both looked into the claims but closed their investigations without any charges, citing a lack of evidence.

Nonetheless, Sia says she’s still not comfortable with Bernad spending unsupervised time with Summi. She says Bernad is not prepared to care for Summi by himself because he was an absentee parent during their marriage, often jetting overseas “at a moment’s notice.”

Sia’s lawyer declined to comment on the proceedings on Tuesday. A rep for Bernad did not immediately return a request for comment.