Marlon van Wyk, 26, entered a plea and sentencing agreement before Judge Robert Henney in the Western Cape High Court.
Van Wyk admitted to unlawfully and intentionally killing 26-year-old Sinodia Schutt in her Saldanha home last February.
He alleged that the killing was done in conspiracy with his co-accused Sharif Padaychee and Jerome Januarie, who were also in court.
In return for the plea, the State withdrew two charges against him, including robbery with aggravating circumstances.
Padaychee and Januarie did not enter agreements with the State and would appear again on August 8 for a pre-trial conference.
Charges against a fourth accused Ricardo Williams were withdrawn last week.
Van Wyk, dressed in a tracksuit, bowed his head and closed his eyes while standing as prosecutor Romay van Rooyen read out the facts accompanying his plea.
According to the plea and sentencing agreement, Padaychee instructed Van Wyk and Januarie to murder Schutt in exchange for five grams of Tik (methamphetamine) and R40,000.
On February 26 last year, Schutt opened the door for Van Wyk and Januarie. They all used Tik.
With her permission, the men then went to her bathroom to use Mandrax and smoke dagga, while she went to the shop to buy cigarettes.
According to the document, she returned and Van Wyk strangled her from behind until she was unconscious.
Van Wyk alleged that Januarie then struck Schutt with a sharp weapon or panga.
After she had died from her injuries, he said he also struck her once with the weapon.
They then fled the house.
Judge Robert Henney confirmed that Van Wyk had entered into the agreement willingly and understood its contents and consequences.
He read out the aggravating circumstances of the crime.
He said Van Wyk had known Schutt, she was a vulnerable person who could not have protected herself against the men, and that the crime was serious.
In mitigation, Van Wyk had admitted guilt, was remorseful, had a young family to support, and had been under the influence of drugs.
His testimony would be used by the State against the other accused.
Henney was satisfied that these circumstances justified a deviation from the minimum sentence of life imprisonment.