diff --git a/phys2bids/physio_obj.py b/phys2bids/physio_obj.py
index 61bdd88eb..3466aa626 100644
--- a/phys2bids/physio_obj.py
+++ b/phys2bids/physio_obj.py
@@ -4,6 +4,7 @@
 """I/O objects for phys2bids."""
 
 import logging
+from copy import deepcopy
 from itertools import groupby
 
 import numpy as np
@@ -228,16 +229,16 @@ class BlueprintInput():
     def __init__(self, timeseries, freq, ch_name, units, trigger_idx,
                  num_timepoints_found=None, thr=None, time_offset=0):
         """Initialise BlueprintInput (see class docstring)."""
-        self.timeseries = is_valid(timeseries, list, list_type=np.ndarray)
-        self.freq = has_size(is_valid(freq, list,
+        self.timeseries = deepcopy(is_valid(timeseries, list, list_type=np.ndarray))
+        self.freq = deepcopy(has_size(is_valid(freq, list,
                                       list_type=(int, float)),
-                             self.ch_amount, 0.0)
-        self.ch_name = has_size(ch_name, self.ch_amount, 'unknown')
-        self.units = has_size(units, self.ch_amount, '[]')
-        self.trigger_idx = is_valid(trigger_idx, int)
-        self.num_timepoints_found = num_timepoints_found
-        self.thr = thr
-        self.time_offset = time_offset
+                             self.ch_amount, 0.0))
+        self.ch_name = deepcopy(has_size(ch_name, self.ch_amount, 'unknown'))
+        self.units = deepcopy(has_size(units, self.ch_amount, '[]'))
+        self.trigger_idx = deepcopy(is_valid(trigger_idx, int))
+        self.num_timepoints_found = deepcopy(num_timepoints_found)
+        self.thr = deepcopy(thr)
+        self.time_offset = deepcopy(time_offset)
 
     @property
     def ch_amount(self):
@@ -456,7 +457,7 @@ def check_trigger_amount(self, thr=None, num_timepoints_expected=0, tr=0):
         # Use the trigger channel to find the TRs,
         # comparing it to a given threshold.
         trigger = self.timeseries[self.trigger_idx]
-        time = self.timeseries[0].copy()
+        time = self.timeseries[0]
         LGR.info(f'The trigger is in channel {self.trigger_idx}')
         # Check that trigger and time channels have the same length.
         # If not, resample time to the length of the trigger
@@ -586,12 +587,12 @@ class BlueprintOutput():
 
     def __init__(self, timeseries, freq, ch_name, units, start_time, filename=''):
         """Initialise BlueprintOutput (see class docstring)."""
-        self.timeseries = is_valid(timeseries, np.ndarray)
-        self.freq = is_valid(freq, (int, float))
-        self.ch_name = has_size(ch_name, self.ch_amount, 'unknown')
-        self.units = has_size(units, self.ch_amount, '[]')
-        self.start_time = start_time
-        self.filename = is_valid(filename, str)
+        self.timeseries = deepcopy(is_valid(timeseries, np.ndarray))
+        self.freq = deepcopy(is_valid(freq, (int, float)))
+        self.ch_name = deepcopy(has_size(ch_name, self.ch_amount, 'unknown'))
+        self.units = deepcopy(has_size(units, self.ch_amount, '[]'))
+        self.start_time = deepcopy(start_time)
+        self.filename = deepcopy(is_valid(filename, str))
 
     @property
     def ch_amount(self):
diff --git a/phys2bids/tests/test_physio_obj.py b/phys2bids/tests/test_physio_obj.py
index 4fc1ae6d9..b28be27ba 100644
--- a/phys2bids/tests/test_physio_obj.py
+++ b/phys2bids/tests/test_physio_obj.py
@@ -89,7 +89,7 @@ def test_BlueprintInput():
     test_time = np.array([0, 1, 1, 2, 3, 5, 8, 13])
     test_trigger = np.array([0, 1, 0, 0, 0, 0, 0, 0])
     test_chocolate = np.array([1, 0, 0, 1, 0, 0, 1, 0])
-    test_timeseries = [test_time.copy(), test_trigger, test_chocolate]
+    test_timeseries = [test_time, test_trigger, test_chocolate]
     test_freq = [42.0, 3.14, 20.0]
     test_chn_name = ['time', 'trigger', 'chocolate']
     test_units = ['s', 's', 'sweetness']
@@ -101,11 +101,12 @@ def test_BlueprintInput():
 
     # Tests rename_channels
     new_names = ['trigger', 'time', 'lindt']
-    blueprint_in.rename_channels(new_names.copy())
+    blueprint_in.rename_channels(new_names)
     assert blueprint_in.ch_name == ['time', 'trigger', 'lindt']
 
     # Tests return_index
     test_index = blueprint_in.return_index(1)
+    assert test_index[0] is not test_trigger
     assert (test_index[0] == test_trigger).all()
     assert test_index[1] == len(test_timeseries)
     assert test_index[2] == test_freq[1]
@@ -140,7 +141,7 @@ def test_cta_time_interp():
     """Test BlueprintInput.check_trigger_amount with time resampling."""
     test_time = np.array([0, 7])
     test_trigger = np.array([0, 1, 0, 0, 0, 0, 0, 0])
-    test_timeseries = [test_time.copy(), test_trigger]
+    test_timeseries = [test_time, test_trigger]
     test_freq = [42.0, 3.14]
     test_chn_name = ['time', 'trigger']
     test_units = ['s', 's']