"I am certain there is more evidence out there to convict the right men of the right crimes in Scarlett's case. An Indian man tried to make contact with me to tell me he saw Scarlett with some men on the night she died, she was trying to get away and he went to help but they threatened him and he left," Ms Mackeown said on crowdfunding site www.justgiving.com while making a pitch for the money.
"I was also told by a respectable person that there was a video containing evidence connected to Scarlett's murder and the minister's son," she said.
Last year, a trial court in Goa acquitted two beach shack workers of culpable homicide and sexual assault charges due to lack of evidence, following a two-year long investigation and a six-year trial.
According to documents which were brought on record by the prosecution during the trial, Scarlett was allegedly sexually assaulted by Samson D'Souza and Placido Carvalho in February 2008 after allegedly plying her with drugs and left to die at the Anjuna beach.
The case was first investigated by the Goa Police, whose probe was riddled with inconsistencies and constant petitioning by Ms Mackeown resulted in the case being transferred to the Central Bureau of Investigation.
But Ms Mackeown, in her letter to Prime Minister Narendra Modi some months back, had suggested that the CBI probe was compromised.
"I feel like the authorities in India are just going through the motions as ours was a very public case but dragging it out to wear us as a family down and hope the public forget. The truth can not be exposed with half an investigation as those that tried to cover up Scarlett's murder were never investigated due to political connections," she has also said in the appeal.