There are multiple bands with the name Witness:

1) Witness is a Hardcore band from Mountain Lakes, New Jersey that started in the winter of 2009. They have a self‑released demo «Embrace Your Nihilist Self» out now. They also have their debut 7" due out summer 2010.
Members:
Corey DiPrimo- Guitar
Dylan Morris- Drums
Eddie Cuddy- Guitar
Marke DeCristoforo- Vocals
Ryan Cantwell- Bass
Vixen. Fan‑favorite catchy songs include «You're Not My Lover», «When It Comes From The Heart» and «Desperate Lover».

4) Witness is a Christian hip‑hop and reggae artist from Birmingham, West Midlands. He is known for his uplifting and anti‑violence lyrics, as shown in his track «Tooled Up For School». It is also known that Witness has performed in various Midlands schools including Wodensborough CTC in Wednesbury in order to spread his message and promote his work.