Nima Momeni's defense attorney says this has never been a case of who done it, but rather what happened.
Momeni will remain in custody without bail. A judge granted prosecutors' motion to detain Momeni even though the judge said he did not belive Momeni is a flight risk.
"Anyone who is capable of violently killing someone in society is a public safety risk," said Brooke Jenkins, San Francisco District Attorney.
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Momeni's defense attorney is Paula Canny.
"My defense is it's a combination of an accident and self-defense," said Canny.
"It was an accident with three stab wounds?," asked ABC7 News I-Team reporter Melanie Woodrow.
"I'm going to say my defense is, it is an accident... a cross between self-defense and an accident. There was no premeditation deliberation," said Canny.
"We believe that this was an intentional killing," said Jenkins.
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Prosecutors say the knife used to kill Lee came from Nima Momeni's sister Khazar's apartment.
"Mr. Momeni's DNA is on the handle of that knife," said Jenkins.
Khazar Momeni's attorney tells ABC7 News she was friends with Lee but that they did not have a romantic relationship.
In a statement, Khazar Momeni said she was deeply saddened by the decision to keep her brother in custody.
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Canny says had police talked to Nima Momeni the night of the murder, he would have explained what happened and that the case may not have been charged.
"I don't know what I'm missing but I guarantee I'm going to figure out why basic police steps weren't done in this case," said Canny.
"During that nine days, they had to make investigative decisions on who they interviewed," said Jenkins.
"That was a police investigative decision," she continued.
SFPD tells ABC7 News it can't comment on the investigative process while the case is being adjudicated.
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Canny also said Momeni did not immediately know the severity of Lee's injuries and that the vehicle Lee approached after he was stabbed was an Uber Lee called to pick him up.
"He walked away completely fine," said Canny.
Prosecutors say Momeni's sister has declined to be interviewed. Prosecutors and Momeni's defense attorney are back in court Friday to set a preliminary hearing date.
Momeni is accused of stabbing Lee in San Francisco's South of Market neighborhood in the early morning hours of April 4.
Prosecutors claim it happened over a confrontation between the two over Momeni's sister.