diff --git a/common/filters.py b/common/filters.py
index 8ab93a0d..346f76f1 100644
--- a/common/filters.py
+++ b/common/filters.py
@@ -1,6 +1,8 @@
 from abc import ABC, abstractmethod
 import logging
 
+from common.exceptions import BadRequestError
+
 log = logging.getLogger()
 
 
@@ -27,6 +29,13 @@ def __init__(self, field, value, operation):
         self.value = value
         self.operation = operation
 
+        if self.operation == "in":
+            if not isinstance(self.value, list):
+                raise BadRequestError(
+                    "When using the 'in' operation for a WHERE filter, the values must"
+                    " be in a list format e.g. [1, 2, 3]"
+                )
+
     def _extract_filter_fields(self, field):
         fields = field.split(".")
         include_depth = len(fields)
diff --git a/common/icat/filters.py b/common/icat/filters.py
index b80dab45..5d6d99f4 100644
--- a/common/icat/filters.py
+++ b/common/icat/filters.py
@@ -35,7 +35,11 @@ def apply_filter(self, query):
         elif self.operation == "gte":
             where_filter = self.create_condition(self.field, ">=", self.value)
         elif self.operation == "in":
-            where_filter = self.create_condition(self.field, "in", tuple(self.value))
+            # Convert self.value into a string with brackets equivalent to tuple format.
+            # Cannot convert straight to tuple as single element tuples contain a 
+            # trailing comma which Python ICAT/JPQL doesn't accept
+            self.value = str(self.value).replace("[", "(").replace("]", ")")
+            where_filter = self.create_condition(self.field, "in", self.value)
         else:
             raise FilterError(f"Bad operation given to where filter: {self.operation}")
 
@@ -65,9 +69,10 @@ def create_condition(attribute_name, operator, value):
         """
 
         conditions = {}
-        # Removing quote marks when doing conditions with IN expressions
+        # Removing quote marks when doing conditions with IN expressions or when a
+        # distinct filter is used in a request
         jpql_value = (
-            f"{value}" if isinstance(value, tuple) or operator == "!=" else f"'{value}'"
+            f"{value}" if operator == "in" or operator == "!=" else f"'{value}'"
         )
         conditions[attribute_name] = f"{operator} {jpql_value}"
         log.debug("Conditions in ICAT where filter, %s", conditions)