A fourth person denied five non-racing charges and also elected to face a jury trial.
They will all be back in court on March 25, when another nine harness racing figures arrested after Operation Inca will appear for a Crown case review hearing.
The charges came after raids on multiple stables and properties in Canterbury, Invercargill, Manawatu and Auckland late last year.
In December, a male driver in his 50s was charged with conspiring with another person to manipulate a race result last year by "administering a substance" to a horse before the race "in order to gain a pecuniary advantage, namely the winning stakes". He denied the charge and elected trial by jury.
North Canterbury trainer Andrew Douglas Stuart, 42, faces four race-fixing allegations, while Graham Henry Beirne, a 71-year-old Christchurch man, has previously denied two race fixing charges and is yet to enter a plea on a third charge.
A 40-year old Canterbury man denies three race-fixing charges and is yet to enter pleas on three unrelated drugs charges.
Three other men – aged 50, 35 and 26 – deny race-fixing allegations, as does Palmerston North man Brent Stephen Wall, 47, and 44-year-old Rolleston-based horse trainer Nigel Raymond McGrath.
Others face drugs charges that their lawyers say is unconnected to the horse racing investigation, including Elie Sawma, a 42-year-old Christchurch hairdresser charged with supplying the Class B controlled drug MDMA, possession of MDMA, and offering to supply the Class A drug cocaine.