ALLEGED stun gun killer Sarah Williams has said there was no plot with her friend to murder Helmshore businesswoman Sadie Hartley.

Her co-defendant, Katrina Walsh, 56, is said to have played a key role in helping Williams, 35, to "get rid of" her love rival and kept a diary of their plans as they developed.

But Williams told a jury at Preston Crown Court she had no idea what Walsh put in her diary entries and she had "no control or interest whatsoever" in them.

The Crown say Williams' obsessive desire for Ms Hartley's partner, Ian Johnston, 57, led to her knifing Ms Hartley to death on the early evening of January 14 this year.

The 60-year-old victim had been incapacitated beforehand with a 500,000-volt stun gun as she opened the front door of her £500,000 detached property in Helmshore, Lancashire.

It is alleged that Williams placed a tracking device on Mr Johnston's car in the weeks before the murder and discovered that the couple were living together in Sunny Bank Road, Helmshore.

On Thursday, Williams told the court it was Walsh's idea to buy the stun gun and the tracker and she did not know that the horse riding instructor had bought the murder weapon.

Her barrister, Gordon Cole QC, took her through entries recorded in diaries that were recovered at Walsh's workplace.

In September 2014, Walsh wrote: "Sarah came round so got caught up in endless murder plots for Ian's other half."

Mr Cole asked Williams: "Were there any murder plots discussed between you and Katrina Walsh?"

The defendant replied: "No, not at any time in any way."

Another diary entry from Walsh was: "We're also seriously talking of getting rid of her opponent. I agree is probably a good play ... she does seem to be a totally evil bitch."

Mr Cole said to Williams: "Have you any idea why she wrote things like that?"

She said: "I couldn't account for what she wrote and why."

The jury has heard that the two defendants visited Germany on December 10 last year where the stun gun used in the murder was purchased.

Williams said the plan for the journey was to visit a Celtic museum and the Christmas markets but that Walsh instead took her to a shop and bought the stun gun.

Mr Cole asked: "Did you know the reason for the purchase?"

She replied: "I asked and the reason was that it would be good for self-defence."

Williams said she thought Walsh bought the tracker because of her "excessive and obsessive" interest in the Channel 4 programme Hunted - in which teams of people try to avoid detection by "going off the grid".

Williams, of Treborth Road, Blacon, Chester, and Walsh, of Hare Lane, Chester, both deny murder.