Lindsay Clancy: Day 3 of Trial of Mom Accused of Killing 3 Children

The trial for Lindsay Clancy -- the Massachusetts mother accused of brutally murdering her three young children -- continued Thursday with multiple first responders testifying to the horror they came upon.

Multiple paramedics took the stand ... and described finding the three dead young children in ghastly detail ... and described their efforts to revive the victims.

Opening statements were Monday in a horrific case ... and Clancy's ex-husband Patrick took the stand, and he defended her ... which he continued to do on the second day.

Yesterday was particularly dramatic because the court heard the frantic 911 call made by Patrick upon discovering Lindsey suffering from severe injuries after she tried to kill herself ... before he discovered she also allegedly murdered their three children.

Lindsay reportedly sobbed in court while the 7-minute call was played.

Patrick also detailed in court the horrifying scene as he saw it ... including blood "everywhere" in the room, saying it looked like it was sprayed with a hose.

Clancy is accused of strangling Cora, 5, Dawson, 3, and 8-month-old Callan with elastic workout bands at her Duxbury, Massachusetts home.

Lindsay's lawyers are expected to make a case for insanity, intending to argue the mom was experiencing postpartum psychosis when she allegedly brutally killed her kids. Patrick is helping with that defense.