Help needed to file a complaint on my father abusing my mother

My father has been physically, emotionally, verbally, economically abusing my mother from the past 30 years. He restricted her to contact my maternal side. He has no job and from the past 30 years my mother has been working as a Staff Nurse in a Government hospital and has been the bread earner of our family. He drinks a lot and abuses my mother every time. She has been through every type of torture like beaten and broke her head by an iron rod, couldn't use index finger because he pressed it in a cutting plier number of times, she has injuries all over her body. As we are three daughters my mother held back, thinking about our future and career. He has been restricting her to use her own earnings on her will. He maintains the house hold budget and gives little or no money to my mother and us. We have been suffering since years but kept quiet because my mother wanted us to have good future. But now my mother has developed diabetes and BP and she has been sick. She couldn't take any of the abuse anymore. She has almost mentally died and couldn't not remember certain things showing the signs of dementia. We have summon up our courage and finally want to speak out. If not, my father will kill my mother any day. We need an advice how to approach to lodge a complaint. Can we three daughters be the witnesses? or neighbors should be the witnesses. We have moved houses from time to time because of him. We can get witnesses from my neighborhood. Please help me to do it at the least for my mother. I want to protect her at any cost. Thanks in advance.