A Texas jury was set to continue deliberations on Tuesday in the trial of a white former police officer accused of murdering a black neighbour in his own apartment.

Amber Guyger fatally shot Botham Jean in his apartment in Dallas on 6 September last year. The 31-year-old claimed she parked on the wrong floor of the complex by mistake and entered Jean’s flat, thinking it was hers.

In emotional testimony last week, Guyger said she shot the 26-year-old because she thought he was an intruder and feared for her life. She was fired from the Dallas police department and indicted on a murder charge.

The jury have been sequestered because of the high profile of the case. Jean’s death was widely covered in the media and prompted protests in Dallas against police brutality and racism.

Jurors spent several hours deliberating on Monday, the seventh day of the trial. They have to decide if Guyger has a valid defence under Texas’ so-called “castle doctrine”, a stand-your-ground law. Judge Tammy Kemp controversially ruled on Monday that it could factor into their deliberations.

The law allows for the use of deadly force in self-defence by civilians on their property. Guyger’s lawyers argued that she thought she was in her home when she killed Jean and sincerely believed her life was under threat.

A prosecutor, Jason Fine, told the jury the “castle doctrine” should not apply: “It protects homeowners against intruders – and now all of a sudden the intruder is trying to use it against the homeowner.”

He described much of her testimony as “garbage”, arguing that it was absurd for a trained police officer to miss numerous signs in the complex that she was one floor too high, and that Jean, who was unarmed and settling down on his couch to watch television and eat ice cream, did not represent an urgent deadly threat.

Rather than act reasonably, prosecutors alleged, once she decided there was an intruder in “her” apartment she burst in like a “commando”, fully intending to shoot.

Guyger pleaded not guilty. Murder carries a potential life sentence, but Kemp allowed the jury to consider convicting her of manslaughter, which typically carries a sentence of between two and 20 years.