Story highlights Hilton Botha was pulled from the Pistorius murder case last month

Prosecutors reinstated attempted murder charges against Botha in a 2011 case

Botha was the first detective on the scene of Reeva Steenkamp's shooting death

Sprinter Oscar Pistorius is accused in the killing of his girlfriend

Hilton Botha, the former lead detective in the Oscar Pistorius murder case, cited "private reasons" for resigning from the police force, South African Police spokesman Brig. Neville Malila said Thursday.

Botha was pulled from the Pistorius case last month after prosecutors reinstated attempted murder charges against him in a 2011 case. The 22-year South African Police veteran is accused of chasing and firing on a minibus full of people while drunk. He is charged with seven counts of attempted murder.

Pistorius, the 26-year-old double amputee track star, is accused in the killing of his girlfriend, Reeva Steenkamp , 29, last month.

Botha, the first officer on the scene of the Valentine's Day shooting, handed in his resignation Wednesday, Malila said.

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"We are not going into the reasons," Malila said. "He has indicated to us it is for private reasons."

His removal from the high-profile murder case came just days after his testimony at a bail hearing for Pistorius that included admissions that police could have contaminated the crime scene and failed to properly catalog evidence.

The sprinter said in an affidavit that he thought an intruder was hiding in a toilet room inside the bathroom of his Pretoria home. He fired into the room in a fit of terror before realizing the person inside was Steenkamp, Pistorius said.

During the three-day bail hearing, held in a dark, stuffy Pretoria courtroom, defense attorney Barry Roux hammered away at the credibility of Botha and the entire police investigation.

He argued that police had missed a bullet in the toilet of the bathroom where Steenkamp was shot and may have contaminated the crime scene by failing to wear protective foot covers.

Botha told Roux that investigators didn't wear the booties because they'd run out.

Bulelwa Makeke, the spokeswoman for South Africa's National Prosecuting Authority, said before the announcement of Botha's removal that the accusations against the investigator would be little more than a "speed bump" in the Pistorius case.

The attempted murder charges against Botha had previously been withdrawn for additional investigation, but prosecutors decided last month to proceed, South African Police Service Commissioner Riah Phiyega said.

Phiyega praised Botha, saying he is an experienced investigator who "has presented the case of the police well."

Botha was replaced by the department's most senior detective, Vinesh Moonoo, in a move Phiyega said positioned the department for a "long-haul" investigation of Steenkamp's killing.