The case relates to a 'County Lines' operation masterminded by traffickers based in Liverpool to ply illegal drugs to addicts in the Midlands.
Clare Ring, 48, Erin Vesayaporn, and 38, both from Shrewsbury, and Shaun King, 21, from Merseyside, deny conspiracy to supply Class A drugs and offences of being concerned in the supply of Class A drugs in 2015.
A jury at Shrewsbury Crown Court heard that numerous other defendants were involved and some had admitted their roles in the conspiracy.
Prosecuting barrister Mr Graham Russell said in the case of these three defendants, it was for the jury to decide whether each of them had agreed to conspire to supply drugs along with the others.
Those who have admitted to the offence include Adrian Harley, Kelly Carter, Zac Dillon, Gary Cox, Anthony Gray, Jordan Gray and Dean Pritchard.
Mr Russell told the jury: “The nature of the supply is referred to as County Lines, a term which you may be familiar with. It refers to organised crime gangs which run operations to supply controlled drugs from one city to another.
“In this case we are concerned with is such an operation. Heroin and cocaine was trafficked to sell in Shrewsbury. The traffickers in Liverpool rely on local residents to provide them with bases to operate from, transport and contacts.
“Each defendant faces this central charge of conspiracy.”
He said the conspiracy involved use of six mobile telephones referred to as “grafts” which were managed by various defendants including Adrian Harley and used as to make “pool” calls to contact customers simultaneously.
Mr Rusell said throughout that year some of the pool phones were used in the “heavy lifting” while others stopped operating as soon as certain defendants were arrested and taken into custody, including a number used by Pritchard.
The drugs were advertised in get “three for 25” deals and described as the “fattest and best in town”.
The court heard that Ring, Vesayaporn and King were associates of the other defendants and that King, a teen at the time, was arrested along with Jordan Gray.
Mr Russell said checks of mobile phone activity using cell sites and cross referencing them with automatic number plate technology to link the defendants with the operation.
He said an example of this was evidence was used to identify Anthony Gray, who drove a silver-coloured Audi, and his role in it.
“As a result of the use of the ANPR and mobile phones we are able to see roughly that people travelled in one direction and roughly the direction of travel,” Mr Russell added.
Vesayaporn, of Wayford View, Dorrington, Ring, of Featherbed Lane, Sundorne, and Shaun King, of Liverpool, denied the conspiracy allegations.
They were arrested when West Mercia Police’s serious and organised crime unit launched efforts to disrupt the activity.
The trial continues at Shrewsbury.