Can I contest a will

My mother who lives in Scotland was diagonsed with alzheimers 7 years ago, she was giving the alzheimers memory test but failed it and my 2 sisters were told her alzheimers was to advanced for treatment.
2 years after she was diagnosed sister 1 took my mother from her council flat and moved her daughter in, she refused to give my 2nd sister any information about my mother whom she had moved into a nursing home in a different town. In 2006 sister 1 used my mothers long term renters discount to buy my mother council flat then a month later took my mother to a solicitor and had a will drawn up willing the flat to her under heritable estate, after this sister 1 got power of attorney over my mothers affairs unknow to myself or other sister therefore stopping us from seeing our mothers medical or financial records, I do know that 3 years after the first diagnoses sister 1 took my mother to St. Johns hospital in Livingston were she was giving more tests including another alzheimers memory test which she failed. I live in Canada but was in contact with both my mother and sister and was not told anything about mum buying her flat or willing it to sister 1 until after it was done.
I wondered that given the circumstances of how my sister got my mother to buy her flat then will it to her and that my mother had been suffering from alzheimers for long would it be possible to prove my mothers will invalid due to my mothers lack of mental capacity.

[able1]

Yes it is possible.

If you can show that, you may invalidate the will.

You will almost certainly need a solicitor to help advise on that, or to see if it is truly even possible given the facts.

Thank you for the advice, could I ask another few questions ?
How long after a person passed away does it take to read a will and does the solicitor inform you when this happens? If not how do I find out what is in the will as sister 1 is no longer communicating with myself or my other sister in Scotalnd and therefore we will have no way of knowing when the will is being read and what exactly is in it.
Secondly after a will has been read how long do you have to get legal advice about your options?

You need to act immediately as within weeks or months the matter can be resolved and closed.

If you are not getting proper access to the information you can file in court and seek orders that will keep you informed--it is a bit of a process so having a solicitor is advisable.